Borrowings - Detailed Information on FHLB Advances and Other Borrowings (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Debt Disclosure [Abstract]
Maximum outstanding at any month end	$ 3,575	$ 5,660	$ 4,737	$ 6,841
Average outstanding balance	3,622	4,821	3,800	4,590
Average remaining borrowing capacity	$ 5,295	$ 5,272	$ 5,389	$ 5,124
Weighted average interest rate	0.45%	0.45%	0.44%	0.86%