Securitization Activities - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Assets securitized in a non-cash exchange for loans receivable and held-to-maturity securities	$ 174	$ 104
Net Asset related to Other Continuing Involvement	94		$ 57
Notional amount related to Other Continuing Involvement	1,440		1,200
Fair Value of Retained Interests	2,840		3,350
Other Retained Interests [Member]
Fair Value of Retained Interests	$ 156		$ 149
Weighted average life (years)	2 years 10 months 24 days		3 years 3 months 18 days
Maximum Exposure to Adverse Changes in the value of Other retained interests	$ 156		$ 149