Fair Value Measurement - Estimates Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Financial Assets
Cash and due from banks	$ 593,872	$ 234,796
Equity securities	11,230	12,343
Available-for-sale debt securities	2,262,082	2,393,558
Held-to-maturity debt securities	814,414	851,753
Loans held for sale	48,021	43,013
Accrued interest receivable	43,960	43,648
Financial Liabilities
Deposits	11,043,332	11,004,006
Federal Home Loan Bank borrowings	1,585,608	1,415,615
Other borrowings	333,966	282,362
Subordinated debt and junior subordinated debt	192,008	199,869
Accrued interest payable	7,667	8,077
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial Assets
Cash and due from banks	593,872	234,796
Equity securities	11,230	12,343
Accrued interest receivable	43,960	43,648
Financial Liabilities
Deposits	9,104,011	8,948,086
Other borrowings	334,305	279,345
Accrued interest payable	7,667	8,077
Significant Other Observable Inputs (Level 2) [Member]
Financial Assets
Available-for-sale debt securities	2,260,506	2,391,953
Held-to-maturity debt securities	840,597	873,995
Loans held for sale	48,021	43,013
Other assets - interest rate derivatives	48,182	14,585
Financial Liabilities
Deposits	1,948,782	2,041,732
Federal Home Loan Bank borrowings	1,598,550	1,420,302
Other borrowings		3,346
Subordinated debt and junior subordinated debt	117,046	122,934
Other liabilities - interest rate derivatives	52,464	16,117
Significant Unobservable Inputs (Level 3) [Member]
Financial Assets
Available-for-sale debt securities	1,576	1,605
Held-to-maturity debt securities	523	528
Net loans	10,431,898	10,297,989
Financial Liabilities
Subordinated debt and junior subordinated debt	69,358	65,415
Carrying Amount [Member]
Financial Assets
Cash and due from banks	593,872	234,796
Equity securities	11,230	12,343
Available-for-sale debt securities	2,262,082	2,393,558
Held-to-maturity debt securities	814,178	851,753
Net loans	10,235,324	10,215,556
Loans held for sale	48,021	43,013
Other assets - interest rate derivatives	48,182	14,585
Accrued interest receivable	43,960	43,648
Financial Liabilities
Deposits	11,043,332	11,004,006
Federal Home Loan Bank borrowings	1,585,608	1,415,615
Other borrowings	333,966	282,362
Subordinated debt and junior subordinated debt	192,008	199,869
Other liabilities - interest rate derivatives	52,464	16,117
Accrued interest payable	7,667	8,077
Fair Value Estimate [Member]
Financial Assets
Cash and due from banks	593,872	234,796
Equity securities	11,230	12,343
Available-for-sale debt securities	2,262,082	2,393,558
Held-to-maturity debt securities	841,120	874,523
Net loans	10,431,898	10,297,989
Loans held for sale	48,021	43,013
Other assets - interest rate derivatives	48,182	14,585
Accrued interest receivable	43,960	43,648
Financial Liabilities
Deposits	11,052,793	10,989,818
Federal Home Loan Bank borrowings	1,598,550	1,420,302
Other borrowings	334,305	282,691
Subordinated debt and junior subordinated debt	186,404	188,349
Other liabilities - interest rate derivatives	52,464	16,117
Accrued interest payable	$ 7,667	$ 8,077