Fair Value Measurements - Carrying Amount and Estimated Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Assets
Investment securities available-for-sale	$ 1,802	$ 1,944
Investment securities held-to-maturity	244	393
Loans held-for-sale	5,996	7,009
Loans held-for-investment	12	13
Mortgage servicing rights	340	329
Carrying Value
Assets
Cash and cash equivalents	149	623
Investment securities available-for-sale	1,802	1,944
Investment securities held-to-maturity	236	377
Loans held-for-sale	6,378	7,098
Loans held-for-investment	14,268	16,227
Loans with government guarantees	1,945	2,516
Mortgage servicing rights	340	329
Federal Home Loan Bank stock	377	377
Bank owned life insurance	363	356
Repossessed assets	6	8
Other assets, foreclosure claims	7	17
Derivative financial instruments, assets	204	281
Liabilities
Federal Home Loan Bank advances and other	(3,270)	(5,100)
Long-term debt	(396)	(641)
DOJ Liability		(35)
Derivative financial instruments, liabilities	(30)	(102)
Carrying Value | Demand deposits and savings accounts
Liabilities
Deposits	(8,908)	(8,616)
Carrying Value | Certificates of deposit
Liabilities
Deposits	(988)	(1,355)
Carrying Value | Wholesale deposits
Liabilities
Deposits	(1,301)	(1,031)
Carrying Value | Government deposits
Liabilities
Deposits	(2,450)	(1,765)
Carrying Value | Company controlled deposits
Liabilities
Deposits	(5,688)
Carrying Value | Custodial deposits
Liabilities
Deposits		(7,206)
Estimated Fair Value
Assets
Cash and cash equivalents	149	623
Investment securities available-for-sale	1,802	1,944
Investment securities held-to-maturity	244	393
Loans held-for-sale	6,379	7,098
Loans held-for-investment	14,276	16,188
Loans with government guarantees	1,895	2,498
Mortgage servicing rights	340	329
Federal Home Loan Bank stock	377	377
Bank owned life insurance	363	358
Repossessed assets	6	8
Other assets, foreclosure claims	7	17
Derivative financial instruments, assets	204	281
Liabilities
Federal Home Loan Bank advances and other	(3,286)	(5,124)
Long-term debt	(344)	(596)
DOJ Liability		(35)
Derivative financial instruments, liabilities	(30)	(102)
Estimated Fair Value | Demand deposits and savings accounts
Liabilities
Deposits	(8,121)	(7,864)
Estimated Fair Value | Certificates of deposit
Liabilities
Deposits	(992)	(1,365)
Estimated Fair Value | Wholesale deposits
Liabilities
Deposits	(1,306)	(1,047)
Estimated Fair Value | Government deposits
Liabilities
Deposits	(2,340)	(1,706)
Estimated Fair Value | Company controlled deposits
Liabilities
Deposits	(5,665)
Estimated Fair Value | Custodial deposits
Liabilities
Deposits		(7,133)
Estimated Fair Value | Level 1
Assets
Cash and cash equivalents	149	623
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 and other	0	0
Long-term debt	0	0
DOJ Liability		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
Estimated Fair Value | Level 1 | Custodial deposits
Liabilities
Deposits		0
Estimated Fair Value | Level 2
Assets
Cash and cash equivalents	0	0
Investment securities available-for-sale	1,802	1,944
Investment securities held-to-maturity	244	393
Loans held-for-sale	6,379	7,098
Loans held-for-investment	11	11
Loans with government guarantees	1,895	2,498
Mortgage servicing rights	0	0
Federal Home Loan Bank stock	377	377
Bank owned life insurance	363	358
Repossessed assets	0	0
Other assets, foreclosure claims	7	17
Derivative financial instruments, assets	118	73
Liabilities
Federal Home Loan Bank advances and other	(3,286)	(5,124)
Long-term debt	(344)	(596)
DOJ Liability		0
Derivative financial instruments, liabilities	(29)	(102)
Estimated Fair Value | Level 2 | Demand deposits and savings accounts
Liabilities
Deposits	(8,121)	(7,864)
Estimated Fair Value | Level 2 | Certificates of deposit
Liabilities
Deposits	(992)	(1,365)
Estimated Fair Value | Level 2 | Wholesale deposits
Liabilities
Deposits	(1,306)	(1,047)
Estimated Fair Value | Level 2 | Government deposits
Liabilities
Deposits	(2,340)	(1,706)
Estimated Fair Value | Level 2 | Company controlled deposits
Liabilities
Deposits	(5,665)
Estimated Fair Value | Level 2 | Custodial deposits
Liabilities
Deposits		(7,133)
Estimated Fair Value | Level 3
Assets
Cash and cash equivalents	0	0
Investment securities available-for-sale		0
Investment securities held-to-maturity		0
Loans held-for-sale		0
Loans held-for-investment	14,265	16,177
Loans with government guarantees		0
Mortgage servicing rights	340	329
Federal Home Loan Bank stock		0
Bank owned life insurance		0
Repossessed assets	6	8
Other assets, foreclosure claims		0
Derivative financial instruments, assets	86	208
Liabilities
Federal Home Loan Bank advances and other	0	0
Long-term debt	0	0
DOJ Liability		(35)
Derivative financial instruments, liabilities	(1)	0
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
Estimated Fair Value | Level 3 | Custodial deposits
Liabilities
Deposits		$ 0