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Investment Securities - Realized Gains and Losses on Securities and OTTI Recognized in Earnings (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Realized gains (losses): |  |  |
Gross realized gains | $ 44 | $ 13 | $ 144
Gross realized losses | (18) | (21) | (74)
Net realized gains (losses) | 26 | (8) | 70
OTTI recognized in earnings: |  |  |
Credit related OTTI | 0 | (1) | (2)
Intent-to-sell OTTI | 0 | (200) | (3)
Total OTTI recognized in earnings | 0 | (201) | (5)
Net securities gains (losses) | 26 | (209) | 65
Total proceeds from sales | $ 4,780 | $ 6,399 | $ 8,181

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