Investment Securities - Summary of Unrealized Loss Positions on Investment Securities (Details) $ in Millions	Sep. 30, 2025 USD ($) security	Dec. 31, 2024 USD ($) security
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security	607	609
Fair Value
Less than Twelve Months	$ 913	$ 1,674
Twelve Months or Longer	5,625	5,592
Total	6,538	7,266
Unrealized Loss
Less than Twelve Months	1	3
Twelve Months or Longer	731	929
Total	$ 732	$ 932
Debt Securities | GSE CMOs
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security	230	223
Fair Value
Less than Twelve Months	$ 899	$ 1,636
Twelve Months or Longer	3,037	2,822
Total	3,936	4,458
Unrealized Loss
Less than Twelve Months	1	3
Twelve Months or Longer	370	444
Total	$ 371	$ 447
Debt Securities | U.S. Government agency and GSE obligations
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security	33	33
Fair Value
Less than Twelve Months	$ 0	$ 0
Twelve Months or Longer	1,287	1,203
Total	1,287	1,203
Unrealized Loss
Less than Twelve Months	0	0
Twelve Months or Longer	216	299
Total	$ 216	$ 299
Debt Securities | GSE certificates
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security	326	328
Fair Value
Less than Twelve Months	$ 0	$ 38
Twelve Months or Longer	948	1,040
Total	948	1,078
Unrealized Loss
Less than Twelve Months	0	0
Twelve Months or Longer	126	167
Total	$ 126	$ 167
Debt Securities | Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security	6	11
Fair Value
Less than Twelve Months	$ 0	$ 0
Twelve Months or Longer	157	308
Total	157	308
Unrealized Loss
Less than Twelve Months	0	0
Twelve Months or Longer	7	6
Total	$ 7	$ 6
Debt Securities | Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security	5	5
Fair Value
Less than Twelve Months	$ 14	$ 0
Twelve Months or Longer	142	154
Total	156	154
Unrealized Loss
Less than Twelve Months	0	0
Twelve Months or Longer	4	2
Total	$ 4	$ 2
Debt Securities | Capital trust notes
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security	5	5
Fair Value
Less than Twelve Months	$ 0	$ 0
Twelve Months or Longer	35	33
Total	35	33
Unrealized Loss
Less than Twelve Months	0	0
Twelve Months or Longer	8	10
Total	$ 8	$ 10
Debt Securities | Private Label CMOs
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security	1	2
Fair Value
Less than Twelve Months	$ 0	$ 0
Twelve Months or Longer	14	17
Total	14	17
Unrealized Loss
Less than Twelve Months	0	0
Twelve Months or Longer	0	1
Total	$ 0	$ 1
Debt Securities | Foreign notes
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security		1
Fair Value
Less than Twelve Months		$ 0
Twelve Months or Longer		10
Total		10
Unrealized Loss
Less than Twelve Months		0
Twelve Months or Longer		0
Total		$ 0
Debt Securities | Municipal bonds
Debt Securities, Available-for-sale [Line Items]
Number of Debt Securities | security	1	1
Fair Value
Less than Twelve Months	$ 0	$ 0
Twelve Months or Longer	5	5
Total	5	5
Unrealized Loss
Less than Twelve Months	0	0
Twelve Months or Longer	0	0
Total	$ 0	$ 0