Regulatory Capital Requirements (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Senior preferred stock	$ 120,836	$ 120,836
Net worth	82,000	77,700
Shortfall of available capital	238,000	243,000
Adjusted total capital requirement (including buffers)	188,000	188,000
Adjusted total assets	4,549,000	4,552,000
Risk-weighted assets	1,323,000	1,357,000
Total capital
Available Capital (Deficit)	(30,000)	(34,000)
Minimum Capital Requirement	106,000	109,000
Total Capital Requirement (including Buffers)	$ 106,000	$ 109,000
Available Capital (Deficit) Ratio	(0.023)	(0.025)
Minimum Capital Ratio Requirement	0.080	0.080
Total Capital Requirement Ratio (including Buffers)	0.080	0.080
Common equity tier 1 capital
Available Capital (Deficit)	$ (69,000)	$ (74,000)
Minimum Capital Requirement	60,000	61,000
Total Capital Requirement (including Buffers)	$ 142,000	$ 140,000
Available Capital (Deficit) Ratio	(0.052)	(0.055)
Minimum Capital Ratio Requirement	0.045	0.045
Total Capital Requirement Ratio (including Buffers)	0.107	0.103
Tier 1 capital
Available Capital (Deficit)	$ (50,000)	$ (55,000)
Minimum Capital Requirement	79,000	81,000
Total Capital Requirement (including Buffers)	$ 161,000	$ 160,000
Available Capital (Deficit) Ratio	(0.038)	(0.041)
Minimum Capital Ratio Requirement	0.060	0.060
Total Capital Requirement Ratio (including Buffers)	0.122	0.118
Adjusted total capital
Available Capital (Deficit)	$ (50,000)	$ (55,000)
Minimum Capital Requirement	106,000	109,000
Total Capital Requirement (including Buffers)	$ 188,000	$ 188,000
Available Capital (Deficit) Ratio	(0.038)	(0.041)
Minimum Capital Ratio Requirement	0.080	0.080
Total Capital Requirement Ratio (including Buffers)	0.142	0.139
Core capital
Available Capital (Deficit)	$ (39,000)	$ (43,000)
Minimum Capital Requirement	114,000	114,000
Total Capital Requirement (including Buffers)	$ 114,000	$ 114,000
Available Capital (Deficit) Ratio	(0.009)	(0.009)
Minimum Capital Ratio Requirement	0.025	0.025
Total Capital Requirement Ratio (including Buffers)	0.025	0.025
Tier 1 capital
Available Capital (Deficit)	$ (50,000)	$ (55,000)
Minimum Capital Requirement	114,000	114,000
Total Capital Requirement (including Buffers)	$ 138,000	$ 137,000
Available Capital (Deficit) Ratio	(0.011)	(0.012)
Minimum Capital Ratio Requirement	0.025	0.025
Total Capital Requirement Ratio (including Buffers)	0.030	0.030
Deferred tax assets, net	$ 11,525	$ 11,681
Preferred stock	$ 19,130	$ 19,130
Maximum payout ratio	0	0