Fair Value Measurement - Schedule of Earnings Related to Assets Measured at Fair Value on Nonrecurring Basis (Detail) - Nonrecurring - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans held for investment	$ (75)	$ (76)
Loans held for sale	(1)	0
Other assets	(49)	(11)
Total	$ (125)	$ (87)