Fair Value Measurements - Carrying Amount and Estimated Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Assets
Investment securities available-for-sale	$ 2,010	$ 1,804
Investment securities held-to-maturity	186	209
Loans held-for-sale	3,154	4,920
Loans held-for-investment	21	16
Mortgage servicing rights	523	392
Carrying Value
Assets
Cash and cash equivalents	405	1,051
Investment securities available-for-sale	2,010	1,804
Investment securities held-to-maturity	190	205
Loans held-for-sale	3,475	5,054
Loans held-for-investment	13,236	13,408
Loans with government guarantees	1,256	1,650
Mortgage servicing rights	523	392
Federal Home Loan Bank stock	329	377
Bank owned life insurance	367	365
Repossessed assets	4	6
Other assets, foreclosure claims	11	7
Derivative financial instruments, assets	330	141
Liabilities
Federal Home Loan Bank advances	(1,400)	(3,280)
Long-term debt	(396)	(396)
Derivative financial instruments, liabilities	(94)	(20)
Carrying Value | Demand deposits and savings accounts
Liabilities
Deposits	(9,277)	(9,313)
Carrying Value | Certificates of deposit
Liabilities
Deposits	(898)	(951)
Carrying Value | Wholesale deposits
Liabilities
Deposits	(974)	(1,141)
Carrying Value | Government deposits
Liabilities
Deposits	(1,886)	(2,000)
Carrying Value | Company controlled deposits
Liabilities
Deposits	(4,313)	(4,604)
Estimated Fair Value
Assets
Cash and cash equivalents	405	1,051
Investment securities available-for-sale	2,010	1,804
Investment securities held-to-maturity	186	209
Loans held-for-sale	3,475	5,054
Loans held-for-investment	13,197	13,453
Loans with government guarantees	1,256	1,650
Mortgage servicing rights	523	392
Federal Home Loan Bank stock	329	377
Bank owned life insurance	367	365
Repossessed assets	4	6
Other assets, foreclosure claims	11	7
Derivative financial instruments, assets	330	141
Liabilities
Federal Home Loan Bank advances	(1,395)	(3,288)
Long-term debt	(346)	(340)
Derivative financial instruments, liabilities	(94)	(20)
Estimated Fair Value | Demand deposits and savings accounts
Liabilities
Deposits	(7,972)	(8,469)
Estimated Fair Value | Certificates of deposit
Liabilities
Deposits	(901)	(952)
Estimated Fair Value | Wholesale deposits
Liabilities
Deposits	(952)	(1,137)
Estimated Fair Value | Government deposits
Liabilities
Deposits	(1,748)	(1,904)
Estimated Fair Value | Company controlled deposits
Liabilities
Deposits	(4,264)	(4,580)
Estimated Fair Value | Level 1
Assets
Cash and cash equivalents	405	1,051
Investment securities available-for-sale	0	0
Investment securities held-to-maturity	0	0
Loans held-for-sale	0	0
Loans held-for-investment	0	0
Loans with government guarantees	0	0
Mortgage servicing rights	0	0
Federal Home Loan Bank stock	0	0
Bank owned life insurance	0	0
Repossessed assets	0	0
Other assets, foreclosure claims	0	0
Derivative financial instruments, assets	0	0
Liabilities
Federal Home Loan Bank advances	0	0
Long-term debt	0	0
Derivative financial instruments, liabilities	0	0
Estimated Fair Value | Level 1 | Demand deposits and savings accounts
Liabilities
Deposits	0	0
Estimated Fair Value | Level 1 | Certificates of deposit
Liabilities
Deposits	0	0
Estimated Fair Value | Level 1 | Wholesale deposits
Liabilities
Deposits	0	0
Estimated Fair Value | Level 1 | Government deposits
Liabilities
Deposits	0	0
Estimated Fair Value | Level 1 | Company controlled deposits
Liabilities
Deposits	0	0
Estimated Fair Value | Level 2
Assets
Cash and cash equivalents	0	0
Investment securities available-for-sale	2,010	1,804
Investment securities held-to-maturity	186	209
Loans held-for-sale	3,475	5,054
Loans held-for-investment	21	14
Loans with government guarantees	1,256	1,650
Mortgage servicing rights	0	0
Federal Home Loan Bank stock	329	377
Bank owned life insurance	367	365
Repossessed assets	0	0
Other assets, foreclosure claims	11	7
Derivative financial instruments, assets	307	87
Liabilities
Federal Home Loan Bank advances	(1,395)	(3,288)
Long-term debt	(346)	(340)
Derivative financial instruments, liabilities	(67)	(19)
Estimated Fair Value | Level 2 | Demand deposits and savings accounts
Liabilities
Deposits	(7,972)	(8,469)
Estimated Fair Value | Level 2 | Certificates of deposit
Liabilities
Deposits	(901)	(952)
Estimated Fair Value | Level 2 | Wholesale deposits
Liabilities
Deposits	(952)	(1,137)
Estimated Fair Value | Level 2 | Government deposits
Liabilities
Deposits	(1,748)	(1,904)
Estimated Fair Value | Level 2 | Company controlled deposits
Liabilities
Deposits	(4,264)	(4,580)
Estimated Fair Value | Level 3
Assets
Cash and cash equivalents	0	0
Investment securities available-for-sale	0	0
Investment securities held-to-maturity	0	0
Loans held-for-sale	0	0
Loans held-for-investment	13,176	13,439
Loans with government guarantees	0	0
Mortgage servicing rights	523	392
Federal Home Loan Bank stock	0	0
Bank owned life insurance	0	0
Repossessed assets	4	6
Other assets, foreclosure claims	0	0
Derivative financial instruments, assets	23	54
Liabilities
Federal Home Loan Bank advances	0	0
Long-term debt	0	0
Derivative financial instruments, liabilities	(27)	(1)
Estimated Fair Value | Level 3 | Demand deposits and savings accounts
Liabilities
Deposits	0	0
Estimated Fair Value | Level 3 | Certificates of deposit
Liabilities
Deposits	0	0
Estimated Fair Value | Level 3 | Wholesale deposits
Liabilities
Deposits	0	0
Estimated Fair Value | Level 3 | Government deposits
Liabilities
Deposits	0	0
Estimated Fair Value | Level 3 | Company controlled deposits
Liabilities
Deposits	$ 0	$ 0