One of the Motley Fool's co-founders, David Gardner, has often said that when it comes to the best stocks, "winners keep winning." And you only have to look at David's record as a stock picker to know it's worth listening when he speaks. So we asked three Motley Fool contributors to use this idea -- that great businesses tend to remain great -- to help find some great stock ideas for investors.

Looking for stocks that have already doubled for investors, but still have room to run, these Fools identified three remarkably different companies: Trex Company (TREX 4.30%), Canada Goose Holdings (GOOS 2.44%), and ConocoPhillips (COP -0.61%).

A man holds a small rocket that's beginning to launch.

These stocks are set to rocket even higher. Image source: Getty Images.

Keep reading to learn what sets these winners apart, and why they still have plenty of room to grow and continue rewarding shareholders.

Time to load up on this multibagger

Jason Hall (Trex Company): Since the beginning of 2016, shares of eco-friendly decking maker Trex Company are up 217%. That's more than triple the value in less than two years. If we look even further back -- over the past decade -- Trex shares have gained a remarkable 1,670%.

Yet even with these incredible gains, Trex is still very much a growth stock. Last quarter, Trex saw its profits surge 47% on 19% sales growth, putting it on track for yet another year of double-digit sales and profit growth. The company also announced a new distribution partner in the Midwest, further strengthening its position as the most widely available wood-alternative decking on the market.

Even after the company's big growth, Trex's total sales are still shy of $700 million per year:

TREX Revenue (TTM) Chart

TREX Revenue (TTM) data by YCharts.

Furthermore, plain wood still makes up over 85% of total decking volume sold each year. But as more consumers prioritize a greener choice that requires far less maintenance and can last more than twice as long as wood, Trex is set to continue taking share from wood for years to come.

Here's the best part for anyone looking to buy today: Trex shares are down almost 33% from the all-time high back in September, more than triple the 9% decline for the S&P 500 over that same period. If you're looking for an opportunistic buy on a stock with years of growth ahead of it, Trex should be at the top of your list.

Winter is coming

Dan Caplinger (Canada Goose Holdings): The retail sector has been a minefield lately, with many well-known department-store and concept retailers seeing lackluster results that have sent their shares stumbling. Yet that hasn't been the case for Canada Goose Holdings, a relatively new name for investors that just came public early last year.

The maker of winter wear has a history dating back to the 1950s, but it's come a long way from its initial business of providing vests, raincoats, and snowmobile suits. Now Canada Goose has cast its eye toward the upscale luxury retail segment, offering apparel and accessories tailored for discriminating customers who can afford to pay up to $1,500 for a high-quality heavy coat.

GOOS Chart

GOOS data by YCharts.

A big part of Canada Goose's success has come from its connecting more directly with consumers. Traditionally, the company relied on third-party retailers as an essential part of its distribution chain, selling most of its goods at the wholesale level and thereby accepting somewhat lower margin levels on its sales. Now that the Canada Goose brand has been thrust into the limelight, though, the retailer has shifted to build its own distribution capacity, both through physical stores and with online e-commerce portals. That's had the dual impact of increasing revenue and boosting margin, and that enviable combination has led to gains of 122% for the stock just so far in 2018. With strong momentum heading into another cold winter, Canada Goose looks poised for continued success.

Rocketing off the bottom, but still holding plenty of fuel

Matt DiLallo (ConocoPhillips): The oil price crash that began in late 2014 took shares of ConocoPhillips down with it. The U.S. oil giant's stock plunged from a peak of more than $85 a share that summer to a bottom in the low-$30s by February of 2016. Shares, however, have since gone on to rebound more than 100% from that bottom, fueled by higher oil prices, and the company's strategic initiatives to bolster its financial profile.

While the oil giant's stock is up sharply in the past couple of years, it still has plenty of upside. The company spent the past few years repositioning its business so that it could thrive on lower oil prices. As a result, ConocoPhillips only needs oil to average $50 per barrel to provide the funding to cover its dividend, as well as to invest in new wells that should grow its cash flow at a 10% compound annual growth rate on a per-share basis. That focus on expanding cash flow could increase shareholder value in the coming years, even if oil prices remain volatile.

COP Chart

COP data by YCharts.

Another value driver is the company's share-repurchase program. ConocoPhillips is currently in the process of buying back $15 billion in stock, which could retire as much as 20% of its outstanding shares. That repurchase program is one of the factors that enabled the company to make more money last quarter on a per-share basis than it did when oil was over $100 per barrel.

Add ConocoPhillips' cash-flow-focused expansion plan to its needle-moving share-repurchase program, and the oil giant should have plenty of fuel to continue growing shareholder value in the years ahead.