Fair Value Measurement - Estimates Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial Assets
Cash and due from banks	$ 234,796	$ 169,186
Equity securities	12,343	11,737
Available-for-sale debt securities	2,393,558	2,114,129
Held-to-maturity debt securities	851,753	1,020,934
Net loans	10,215,556	7,607,333
Loans held for sale	43,013	8,994
Accrued interest receivable	43,648	38,853
Financial Liabilities
Deposits	11,004,006	8,831,633
Federal Home Loan Bank borrowings	1,415,615	1,054,174
Other borrowings	282,362	290,522
Subordinated debt and junior subordinated debt	199,869	189,842
Accrued interest payable	8,077	4,627
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial Assets
Cash and due from banks	234,796	169,186
Equity securities	12,343	11,737
Accrued interest receivable	43,648	38,853
Financial Liabilities
Deposits	8,948,086	7,376,023
Other borrowings	279,345	288,918
Accrued interest payable	8,077	4,627
Significant Other Observable Inputs (Level 2) [Member]
Financial Assets
Available-for-sale debt securities	2,391,953	2,112,626
Held-to-maturity debt securities	873,995	1,020,195
Loans held for sale	43,013	8,994
Other assets—interest rate derivatives	14,585	4,650
Financial Liabilities
Deposits	2,041,732	1,460,367
Federal Home Loan Bank borrowings	1,420,302	1,051,401
Other borrowings	3,346	1,936
Subordinated debt and junior subordinated debt	188,349	174,448
Other liabilities—interest rate derivatives	16,117	5,081
Significant Unobservable Inputs (Level 3) [Member]
Financial Assets
Available-for-sale debt securities	1,605	1,503
Held-to-maturity debt securities	528	548
Net loans	10,297,989	7,422,825
Carrying Amount [Member]
Financial Assets
Cash and due from banks	234,796	169,186
Equity securities	12,343	11,737
Available-for-sale debt securities	2,393,558	2,114,129
Held-to-maturity debt securities	851,753	1,020,934
Net loans	10,215,556	7,607,333
Loans held for sale	43,013	8,994
Other assets—interest rate derivatives	14,585	4,650
Accrued interest receivable	43,648	38,853
Financial Liabilities
Deposits	11,004,006	8,831,633
Federal Home Loan Bank borrowings	1,415,615	1,054,174
Other borrowings	282,362	290,522
Subordinated debt and junior subordinated debt	199,869	189,842
Other liabilities—interest rate derivatives	16,117	5,081
Accrued interest payable	8,077	4,627
Fair Value Estimate [Member]
Financial Assets
Cash and due from banks	234,796	169,186
Equity securities	12,343	11,737
Available-for-sale debt securities	2,393,558	2,114,129
Held-to-maturity debt securities	874,523	1,020,743
Net loans	10,297,989	7,422,825
Loans held for sale	43,013	8,994
Other assets—interest rate derivatives	14,585	4,650
Accrued interest receivable	43,648	38,853
Financial Liabilities
Deposits	10,989,818	8,836,390
Federal Home Loan Bank borrowings	1,420,302	1,051,401
Other borrowings	282,691	290,854
Subordinated debt and junior subordinated debt	188,349	174,448
Other liabilities—interest rate derivatives	16,117	5,081
Accrued interest payable	$ 8,077	$ 4,627