Fair Value of Assets and Liabilities - Carrying Amount and Estimated Fair Value of Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financial assets
Debt securities, held-to-maturity	$ 3,038,467	$ 3,274,792
Carrying Amount
Financial assets
Cash and cash equivalents	1,672,094	401,995
Debt securities, held-to-maturity	3,553,805	3,715,052
Loans receivable, net of ACL	15,942,775	15,064,529
Total financial assets	21,168,674	19,181,576
Financial liabilities
Term deposits	2,742,017	880,589
FRB Bank Term Funding	2,740,000
FHLB advances		1,800,000
Repurchase agreements and other borrowed funds	1,573,448	1,023,209
Subordinated debentures	132,903	132,782
Total financial liabilities	7,188,368	3,836,580
Estimated Fair Value | Level 1
Financial assets
Cash and cash equivalents	1,672,094	401,995
Debt securities, held-to-maturity	0	0
Loans receivable, net of ACL	0	0
Total financial assets	1,672,094	401,995
Financial liabilities
Term deposits	0	0
FRB Bank Term Funding	0
FHLB advances		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	3,038,467	3,274,792
Loans receivable, net of ACL	0	0
Total financial assets	3,038,467	3,274,792
Financial liabilities
Term deposits	2,780,108	874,850
FRB Bank Term Funding	2,731,093
FHLB advances		1,799,936
Repurchase agreements and other borrowed funds	1,573,448	1,023,209
Subordinated debentures	117,867	122,549
Total financial liabilities	7,202,516	3,820,544
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	15,717,799	14,806,354
Total financial assets	15,717,799	14,806,354
Financial liabilities
Term deposits	0	0
FRB Bank Term Funding	0
FHLB advances		0
Repurchase agreements and other borrowed funds	0	0
Subordinated debentures	0	0
Total financial liabilities	$ 0	$ 0