Disclosures About Fair Value of Financial Instruments - Estimated Fair Values of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Carrying Amount	$ 274,600	$ 518,032
Cash and cash equivalents, Estimated Fair Value	274,600	518,032
Debt securities, available for sale	4,144,029	3,791,575
Loans held for sale	3,003	16,254
Total loans and leases receivable, net of allowance for credit losses on loans and leases	13,924,668
Total loans and leases receivable, net of allowance for credit losses on loans and leases	13,924,668	14,414,827
Total loans and leases receivable, net of allowance for credit losses on loans and leases, Estimated Fair Value	13,571,137	14,207,811
FHLB, Federal Reserve Bank and other restricted stock, Carrying Amount	54,553	64,584
FHLB, Federal Reserve Bank and other restricted stock, Estimated Fair Value		64,584
Derivative assets	21,954	27,295
Deposits held	16,415,560	16,777,924
Deposits, Estimated Fair Value	16,343,932	16,777,236
Federal funds purchased, Carrying Amount	700,000	75,000
Federal funds purchased, Estimated Fair Value	700,000	75,000
FHLB advances, Carrying Amount	0	700,000
FHLB advances, Estimated Fair Value		700,000
Other borrowings, Carrying Amount	223,230	223,086
Other borrowings, Estimated Fair Value	219,130	226,585
Subordinated debt, Carrying Amount	181,742	181,673
Subordinated debt, Estimated Fair Value	196,482	204,782
Derivative liabilities	18,370	26,544
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Estimated Fair Value	274,600	518,032
Debt securities, available for sale	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
Deposits, Estimated Fair Value	15,969,368	16,270,586
Federal funds purchased, Estimated Fair Value	700,000	75,000
FHLB advances, Estimated Fair Value		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)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Estimated Fair Value	0	0
Debt securities, available for sale	4,022,176	3,648,690
Loans held for sale	2,496	15,747
Total loans and leases receivable, net of allowance for credit losses on loans and leases, Estimated Fair Value	1,755,758	2,284,325
FHLB, Federal Reserve Bank and other restricted stock, Estimated Fair Value	46,040	64,584
Derivative assets	21,805	27,116
Deposits, Estimated Fair Value	374,564	506,650
Federal funds purchased, Estimated Fair Value	0	0
FHLB advances, Estimated Fair Value		700,000
Other borrowings, Estimated Fair Value	219,130	226,585
Subordinated debt, Estimated Fair Value	196,482	204,782
Derivative liabilities	18,370	26,544
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents, Estimated Fair Value	0	0
Debt securities, available for sale	121,853	142,885
Loans held for sale	507	507
Total loans and leases receivable, net of allowance for credit losses on loans and leases, Estimated Fair Value	11,815,379	11,923,486
FHLB, Federal Reserve Bank and other restricted stock, Estimated Fair Value	0	0
Derivative assets	149	179
Deposits, Estimated Fair Value	0	0
Federal funds purchased, Estimated Fair Value	0	0
FHLB advances, Estimated Fair Value		0
Other borrowings, Estimated Fair Value	0	0
Subordinated debt, Estimated Fair Value	0	0
Derivative liabilities	$ 0	$ 0