Disclosures About Fair Value of Financial Instruments - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Assets:
Cash and cash equivalents, Carrying Amount	$ 3,419,974	$ 455,806
Cash and cash equivalents, Estimated Fair Value	3,419,974	455,806
Debt securities, available for sale	2,746,728	2,961,015
Debt securities, held to maturity	1,178,370	840,259
Debt securities, held to maturity, fair value	1,115,576	793,813
Loans held for sale	150,368	328,312
Total loans and leases receivable, net of allowance for credit losses on loans and leases	13,423,901	15,335,435
Total loans and leases receivable, net of allowance for credit losses on loans and leases, Estimated Fair Value	13,052,491	14,890,823
FHLB, Federal Reserve Bank and other restricted stock, Carrying Amount	126,098	74,196
FHLB, Federal Reserve Bank and other restricted stock, Estimated Fair Value	126,098	74,196
Derivative assets	28,475	44,435
Liabilities:
Deposits held	18,195,364	18,156,953
Deposits, Estimated Fair Value	18,171,737	18,127,338
FHLB advances, Carrying Amount	1,529,839	800,000
FHLB advances, Estimated Fair Value	1,507,761	781,113
Other borrowings, Carrying Amount	123,775	123,580
Other borrowings, Estimated Fair Value	103,388	108,081
Subordinated debt, Carrying Amount	182,161	181,952
Subordinated debt, Estimated Fair Value	160,712	168,441
Derivative liabilities	41,433	42,106
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents, Estimated Fair Value	3,419,974	455,806
Debt securities, available for sale	0	0
Debt securities, held to maturity, fair value	0	0
Loans held for sale	0	0
Total loans and leases receivable, net of allowance for credit losses on loans and leases, Estimated Fair Value	0	0
FHLB, Federal Reserve Bank and other restricted stock, Estimated Fair Value	0	0
Derivative assets	0	0
Liabilities:
Deposits, Estimated Fair Value	14,201,038	13,907,087
FHLB advances, Estimated Fair Value	0	0
Other borrowings, Estimated Fair Value	0	0
Subordinated debt, Estimated Fair Value	0	0
Derivative liabilities	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents, Estimated Fair Value	0	0
Debt securities, available for sale	2,704,363	2,887,749
Debt securities, held to maturity, fair value	475,388	437,680
Loans held for sale	1,005	322
Total loans and leases receivable, net of allowance for credit losses on loans and leases, Estimated Fair Value	962,566	1,323,312
FHLB, Federal Reserve Bank and other restricted stock, Estimated Fair Value	126,098	74,196
Derivative assets	28,421	44,380
Liabilities:
Deposits, Estimated Fair Value	3,970,699	4,220,251
FHLB advances, Estimated Fair Value	1,507,761	781,113
Other borrowings, Estimated Fair Value	103,388	108,081
Subordinated debt, Estimated Fair Value	160,712	168,441
Derivative liabilities	41,433	42,106
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents, Estimated Fair Value	0	0
Debt securities, available for sale	42,365	73,266
Debt securities, held to maturity, fair value	640,188	356,133
Loans held for sale	149,363	327,990
Total loans and leases receivable, net of allowance for credit losses on loans and leases, Estimated Fair Value	12,089,925	13,567,511
FHLB, Federal Reserve Bank and other restricted stock, Estimated Fair Value	0	0
Derivative assets	54	55
Liabilities:
Deposits, Estimated Fair Value	0	0
FHLB advances, Estimated Fair Value	0	0
Other borrowings, Estimated Fair Value	0	0
Subordinated debt, Estimated Fair Value	0	0
Derivative liabilities	$ 0	$ 0