Regulatory Capital Requirements (Details) $ in Millions	Sep. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
Broker-Dealer, Net Capital Requirement, SEC Regulation [Abstract]
Adjusted total assets	$ 4,419,000	$ 4,423,000
Risk-weighted assets	1,467,000	1,411,000
Total capital (statutory)
Available Capital (Deficit) (less than in 2026)	10,000	(3,000)
Minimum Capital Requirement	117,000	113,000
Total Capital Requirement (including Buffers)	$ 117,000	$ 113,000
Available Capital (Deficit) Ratio	0.007	(0.002)
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)	$ (30,000)	$ (41,000)
Minimum Capital Requirement	66,000	63,000
Total Capital Requirement (including Buffers)	$ 143,000	$ 143,000
Available Capital (Deficit) Ratio	(0.020)	(0.029)
Minimum Capital Ratio Requirement	0.045	0.045
Total Capital Requirement Ratio (including Buffers)	0.097	0.102
Tier 1 capital
Available Capital (Deficit)	$ (11,000)	$ (22,000)
Minimum Capital Requirement	88,000	85,000
Total Capital Requirement (including Buffers)	$ 165,000	$ 165,000
Available Capital (Deficit) Ratio	(0.007)	(0.016)
Minimum Capital Ratio Requirement	0.060	0.060
Total Capital Requirement Ratio (including Buffers)	0.112	0.117
Adjusted total capital
Available Capital (Deficit)	$ (11,000)	$ (22,000)
Minimum Capital Requirement	117,000	113,000
Total Capital Requirement (including Buffers)	$ 194,000	$ 193,000
Available Capital (Deficit) Ratio	(0.007)	(0.016)
Minimum Capital Ratio Requirement	0.080	0.080
Total Capital Requirement Ratio (including Buffers)	0.132	0.137
Core capital (statutory)
Available Capital (Deficit) (* less than)	$ 500	$ (12,000)
Minimum Capital Requirement	110,000	111,000
Total Capital Requirement (including Buffers)	$ 110,000	$ 111,000
Available Capital (Deficit) Ratio	0	(0.003)
Minimum Capital Ratio Requirement	0.025	0.025
Total Capital Requirement Ratio (including Buffers)	0.025	0.025
Tier 1 capital
Available Capital (Deficit)	$ (11,000)	$ (22,000)
Minimum Capital Requirement	110,000	111,000
Total Capital Requirement (including Buffers)	$ 132,000	$ 134,000
Available Capital (Deficit) Ratio	(0.002)	(0.005)
Minimum Capital Ratio Requirement	0.025	0.025
Total Capital Requirement Ratio (including Buffers)	0.030	0.030
Senior preferred stock	$ 120,836	$ 120,836