Fair Value Measurement - Estimates Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financial Assets
Cash and due from banks	$ 759,048	$ 905,447
Equity securities	13,123	13,047
Available-for-sale debt securities	2,775,212	1,978,136
Held-to-maturity debt securities	813,740	731,212
Loans held for sale	153,520	168,378
Accrued interest receivable	68,896	66,790
Financial Liabilities
Deposits	13,286,999	12,429,373
Federal Home Loan Bank borrowings	433,984	549,003
Other borrowings	137,218	241,950
Subordinated debt and junior subordinated debt	192,430	192,291
Accrued interest payable	3,224	4,314
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial Assets
Cash and due from banks	759,048	905,447
Equity securities	13,123	13,047
Accrued interest receivable	68,896	66,790
Financial Liabilities
Deposits	11,731,925	10,810,863
Other borrowings	125,925	235,796
Accrued interest payable	3,224	4,314
Significant Other Observable Inputs (Level 2) [Member]
Financial Assets
Available-for-sale debt securities	2,773,701	1,976,601
Held-to-maturity debt securities	839,411	767,720
Loans held for sale	153,520	168,378
Other assets - interest rate derivatives	31,732	46,418
Financial Liabilities
Deposits	1,568,803	1,629,118
Federal Home Loan Bank borrowings	438,211	555,375
Subordinated debt and junior subordinated debt	105,371	105,768
Other liabilities - interest rate derivatives	32,470	49,917
Significant Unobservable Inputs (Level 3) [Member]
Financial Assets
Available-for-sale debt securities	1,511	1,535
Held-to-maturity debt securities	461	463
Net loans	10,540,445	10,802,883
Financial Liabilities
Subordinated debt and junior subordinated debt	66,771	68,684
Carrying Amount [Member]
Financial Assets
Cash and due from banks	759,048	905,447
Equity securities	13,123	13,047
Available-for-sale debt securities	2,775,212	1,978,136
Held-to-maturity debt securities	813,450	730,886
Net loans	10,543,272	10,603,406
Loans held for sale	153,520	168,378
Other assets - interest rate derivatives	31,732	46,418
Accrued interest receivable	68,896	66,790
Financial Liabilities
Deposits	13,286,999	12,429,373
Federal Home Loan Bank borrowings	433,984	549,003
Other borrowings	137,218	241,950
Subordinated debt and junior subordinated debt	192,430	192,291
Other liabilities - interest rate derivatives	32,470	49,917
Accrued interest payable	3,224	4,314
Fair Value Estimate [Member]
Financial Assets
Cash and due from banks	759,048	905,447
Equity securities	13,123	13,047
Available-for-sale debt securities	2,775,212	1,978,136
Held-to-maturity debt securities	839,872	768,183
Net loans	10,540,445	10,802,883
Loans held for sale	153,520	168,378
Other assets - interest rate derivatives	31,732	46,418
Accrued interest receivable	68,896	66,790
Financial Liabilities
Deposits	13,300,728	12,439,981
Federal Home Loan Bank borrowings	438,211	555,375
Other borrowings	125,925	235,796
Subordinated debt and junior subordinated debt	172,142	174,452
Other liabilities - interest rate derivatives	32,470	49,917
Accrued interest payable	$ 3,224	$ 4,314