Investment Securities - Summary of Unrealized Loss Positions on Investment Securities (Details) $ in Millions	Mar. 31, 2022 USD ($) security	Dec. 31, 2021 USD ($) security
Agency - Commercial
Fair Value
Unrealized Loss Position with Duration 12 Months and Over	$ 2	$ 4
Unrealized Loss Position with Duration Under 12 Months	$ 895	$ 143
Number of Securities
Unrealized Loss Position with Duration 12 Months and Over | security	1	2
Unrealized Loss Position with Duration Under 12 Months | security	91	9
Unrealized Loss
Unrealized Loss Position with Duration 12 Months and Over	$ 0	$ 0
Unrealized Loss Position with Duration Under 12 Months	(28)	0
Fair Value
Unrealized Loss Position with Duration 12 Months and Over	0	0
Unrealized Loss Position with Duration Under 12 Months	$ 86	$ 0
Number of Securities
Unrealized Loss Position with Duration 12 Months and Over | security	0	0
Unrealized Loss Position with Duration Under 12 Months | security	24	1
Unrealized Loss
Unrealized Loss Position with Duration 12 Months and Over	$ 0	$ 0
Unrealized Loss Position with Duration Under 12 Months	(2)	0
Agency - Residential
Fair Value
Unrealized Loss Position with Duration 12 Months and Over	0	0
Unrealized Loss Position with Duration Under 12 Months	$ 609	$ 291
Number of Securities
Unrealized Loss Position with Duration 12 Months and Over | security	0	0
Unrealized Loss Position with Duration Under 12 Months | security	87	19
Unrealized Loss
Unrealized Loss Position with Duration 12 Months and Over	$ 0	$ 0
Unrealized Loss Position with Duration Under 12 Months	(34)	(3)
Fair Value
Unrealized Loss Position with Duration 12 Months and Over	0	0
Unrealized Loss Position with Duration Under 12 Months	$ 90	$ 0
Number of Securities
Unrealized Loss Position with Duration 12 Months and Over | security	0	0
Unrealized Loss Position with Duration Under 12 Months | security	43	0
Unrealized Loss
Unrealized Loss Position with Duration 12 Months and Over	$ 0	$ 0
Unrealized Loss Position with Duration Under 12 Months	(2)	0
Municipal obligations
Fair Value
Unrealized Loss Position with Duration 12 Months and Over	0	0
Unrealized Loss Position with Duration Under 12 Months	$ 12	$ 3
Number of Securities
Unrealized Loss Position with Duration 12 Months and Over | security	0	0
Unrealized Loss Position with Duration Under 12 Months | security	5	1
Unrealized Loss
Unrealized Loss Position with Duration 12 Months and Over	$ 0	$ 0
Unrealized Loss Position with Duration Under 12 Months	0	0
Corporate debt obligations
Fair Value
Unrealized Loss Position with Duration 12 Months and Over	0	0
Unrealized Loss Position with Duration Under 12 Months	$ 11	$ 0
Number of Securities
Unrealized Loss Position with Duration 12 Months and Over | security	0	0
Unrealized Loss Position with Duration Under 12 Months | security	4	0
Unrealized Loss
Unrealized Loss Position with Duration 12 Months and Over	$ 0	$ 0
Unrealized Loss Position with Duration Under 12 Months	0	0
Other mortgage-backed securities
Fair Value
Unrealized Loss Position with Duration 12 Months and Over	0	0
Unrealized Loss Position with Duration Under 12 Months	$ 157	$ 147
Number of Securities
Unrealized Loss Position with Duration 12 Months and Over | security	1	1
Unrealized Loss Position with Duration Under 12 Months | security	7	5
Unrealized Loss
Unrealized Loss Position with Duration 12 Months and Over	$ 0	$ 0
Unrealized Loss Position with Duration Under 12 Months	$ (13)	$ (1)