All four of the nation's too-big-to-fail banks have now reported third-quarter earnings. While net income increased on a year-over-year basis for Bank of America (NYSE:BAC), Citigroup (NYSE:C), and Wells Fargo (NYSE:WFC), it fell at JPMorgan Chase (NYSE:JPM), thanks primarily to lower trading revenue.

Lower legal expenses were the saving grace at Bank of America and Citigroup, both of which recorded multibillion-dollar legal settlements in the year-ago period. Beyond this, their performances amounted to a mixed bag. Bank of America continued to be hobbled by lower net interest income, but saw a slight uptick in revenue from its fee-based businesses. Citigroup, by contrast, saw both figures fall compared to the same quarter last year.

JPMorgan Chase turned in the worst performance of the bunch. Pre-tax earnings at the nation's biggest bank by assets dropped by $1.2 billion compared to the year-ago period, fueled by marginally lower net interest income and a sharp decline in noninterest income due to lower trading and mortgage-banking income. The silver lining to JPMorgan Chase's third-quarter performance was a 2.7% reduction in noninterest expenses.

Finally, Wells Fargo turned in the strongest results. Despite the low interest rate environment, the California-based bank grew both net interest and noninterest income on a year-over-year basis. Wells Fargo accomplished the former by expanding its balance sheet, boosting its average earning assets by an impressive $123 billion.

Scroll through the slideshow below for an even briefer overview of these banks' performances last quarter.

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