Loans and Leases - Components (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 82,547	$ 69,001
Allowance for credit losses on loans and leases	(550)	(393)	$ (197)	$ (199)
Total loans and leases held for investment, net	81,997	68,608
Loans held for sale, at fair value	1,305	1,115
Total loans and leases, net	$ 83,302	$ 69,723
Percent of loans held for investment	100.00%	100.00%
Accrued interest receivable	$ 365	$ 292
Mortgage Loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	56,605	54,473
Allowance for credit losses on loans and leases	$ (283)	$ (290)	(176)	(178)
Percent of loans held for investment	68.60%	78.90%
Mortgage Loans: | Multi-family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 38,004	$ 38,130
Percent of loans held for investment	46.00%	55.30%
Mortgage Loans: | Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 10,464	$ 8,526
Percent of loans held for investment	12.70%	12.40%
Mortgage Loans: | One-to-four family first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 5,934	$ 5,821
Percent of loans held for investment	7.20%	8.40%
Mortgage Loans: | Acquisition, development, and construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 2,203	$ 1,996
Percent of loans held for investment	2.70%	2.90%
Other Loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 25,942	$ 14,528
Allowance for credit losses on loans and leases	$ (267)	$ (103)	$ (21)	$ (21)
Percent of loans held for investment	31.40%	21.10%
Other Loans: | Commercial and industrial loans and lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 23,357	$ 12,276
Percent of loans held for investment	28.30%	17.80%
Other Loans: | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 20,217	$ 10,597
Percent of loans held for investment	24.50%	15.40%
Other Loans: | Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 3,140	$ 1,679
Percent of loans held for investment	3.80%	2.40%
Unearned income	$ 88	$ 90
Other Loans: | Specialty finance loans and leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	4,800	4,400
Other Loans: | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans and leases held for investment	$ 2,585	$ 2,252
Percent of loans held for investment	3.10%	3.30%