Assets and Liabilities Measured at Fair Value - Carrying Amount and Fair Values for Other Financial Instruments that are not Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Assets:
HTM debt securities	$ 2,042,912	$ 2,095,620
Carrying Amount
Assets:
HTM debt securities	2,465,133	2,490,848
Loans and leases, net	18,163,910	18,110,684
Liabilities:
Deposits	23,332,009	23,310,611
Long-term debt	324,854	324,823
Fair Value
Assets:
HTM debt securities	2,042,912	2,095,620
Loans and leases, net	17,622,063	17,585,073
Liabilities:
Deposits	23,320,033	23,305,223
Long-term debt	310,182	310,060
Fair Value | Level 1
Assets:
HTM debt securities	17,779	17,950
Loans and leases, net	0	0
Liabilities:
Deposits	0	0
Long-term debt	0	0
Fair Value | Level 2
Assets:
HTM debt securities	2,025,133	2,077,670
Loans and leases, net	0	0
Liabilities:
Deposits	23,320,033	23,305,223
Long-term debt	0	0
Fair Value | Level 3
Assets:
HTM debt securities	0	0
Loans and leases, net	17,622,063	17,585,073
Liabilities:
Deposits	0	0
Long-term debt	$ 310,182	$ 310,060