Fair Value of Assets and Liabilities - Carrying Amount and Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Carrying Amount
Financial assets
Cash and cash equivalents	$ 788,660	$ 1,354,342
Debt securities, held-to-maturity	3,451,583	3,502,411
Loans receivable, net of ACL	16,533,723	16,005,325
Total financial assets	20,773,966	20,862,078
Financial liabilities
Term deposits	3,039,190	2,915,393
FHLB advances	2,140,157
FRB Bank Term Funding		2,740,000
Repurchase agreements and other borrowed funds	1,628,822	1,568,545
Subordinated debentures	132,984	132,943
Total financial liabilities	6,941,153	7,356,881
Estimated Fair Value | Level 1
Financial assets
Cash and cash equivalents	788,660	1,354,342
Debt securities, held-to-maturity	0	0
Loans receivable, net of ACL	0	0
Total financial assets	788,660	1,354,342
Financial liabilities
Term deposits	0	0
FHLB advances	0
FRB Bank Term Funding		0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Total financial liabilities	0	0
Estimated Fair Value | Level 2
Financial assets
Cash and cash equivalents	0	0
Debt securities, held-to-maturity	3,091,194	3,180,194
Loans receivable, net of ACL	0	0
Total financial assets	3,091,194	3,180,194
Financial liabilities
Term deposits	3,077,983	2,955,521
FHLB advances	2,135,901
FRB Bank Term Funding		2,738,031
Repurchase agreements and other borrowed funds	1,628,822	1,568,545
Subordinated debentures	121,821	119,768
Total financial liabilities	6,964,527	7,381,865
Estimated Fair Value | Level 3
Financial assets
Cash and cash equivalents	0	0
Debt securities, held-to-maturity	0	0
Loans receivable, net of ACL	16,545,822	16,133,681
Total financial assets	16,545,822	16,133,681
Financial liabilities
Term deposits	0	0
FHLB advances	0
FRB Bank Term Funding		0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Total financial liabilities	$ 0	$ 0