Borrowings - Detailed Information on FHLB Advances and Other Borrowings (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Debt Disclosure [Abstract]
Maximum outstanding at any month end	$ 5,660	$ 3,230	$ 6,841	$ 3,391
Average outstanding balance	4,821	2,987	4,590	2,933
Average remaining borrowing capacity	$ 5,272	$ 3,776	$ 5,124	$ 3,506
Weighted average interest rate	0.45%	2.40%	0.86%	2.43%