Fair Value Measurement - Estimates Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Financial Assets
Cash and due from banks	$ 194,355	$ 169,186
Equity securities	11,817	11,737
Available-for-sale debt securities	2,129,284	2,114,129
Held-to-maturity debt securities	900,605	1,020,934
Net loans	7,686,995	7,607,333
Loans held for sale	18,649	8,994
Accrued interest receivable	38,450	38,853
Financial Liabilities
Deposits	8,694,928	8,831,633
Federal Home Loan Bank borrowings	1,121,283	1,054,174
Other borrowings	296,148	290,522
Subordinated debt and junior subordinated debt	156,534	189,842
Accrued interest payable	6,559	4,627
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Financial Assets
Cash and due from banks	194,355	169,186
Equity securities	11,817	11,737
Accrued interest receivable	38,450	38,853
Financial Liabilities
Deposits	7,329,812	7,376,023
Other borrowings	293,205	288,918
Accrued interest payable	6,559	4,627
Significant Other Observable Inputs (Level 2) [Member]
Financial Assets
Available-for-sale debt securities	2,127,682	2,112,626
Held-to-maturity debt securities	920,989	1,020,195
Loans held for sale	18,649	8,994
Other assets - interest rate derivatives	13,281	4,650
Financial Liabilities
Deposits	1,365,967	1,460,367
Federal Home Loan Bank borrowings	1,127,210	1,051,401
Other borrowings	3,369	1,936
Subordinated debt and junior subordinated debt	144,410	174,448
Other liabilities - interest rate derivatives	14,774	5,081
Significant Unobservable Inputs (Level 3) [Member]
Financial Assets
Available-for-sale debt securities	1,602	1,503
Held-to-maturity debt securities	545	548
Net loans	7,674,887	7,422,825
Carrying Amount [Member]
Financial Assets
Cash and due from banks	194,355	169,186
Equity securities	11,817	11,737
Available-for-sale debt securities	2,129,284	2,114,129
Held-to-maturity debt securities	900,605	1,020,934
Net loans	7,686,995	7,607,333
Loans held for sale	18,649	8,994
Other assets - interest rate derivatives	13,281	4,650
Accrued interest receivable	38,450	38,853
Financial Liabilities
Deposits	8,694,928	8,831,633
Federal Home Loan Bank borrowings	1,121,283	1,054,174
Other borrowings	296,148	290,522
Subordinated debt and junior subordinated debt	156,534	189,842
Other liabilities - interest rate derivatives	14,774	5,081
Accrued interest payable	6,559	4,627
Fair Value Estimate [Member]
Financial Assets
Cash and due from banks	194,355	169,186
Equity securities	11,817	11,737
Available-for-sale debt securities	2,129,284	2,114,129
Held-to-maturity debt securities	921,534	1,020,743
Net loans	7,674,887	7,422,825
Loans held for sale	18,649	8,994
Other assets - interest rate derivatives	13,281	4,650
Accrued interest receivable	38,450	38,853
Financial Liabilities
Deposits	8,695,779	8,836,390
Federal Home Loan Bank borrowings	1,127,210	1,051,401
Other borrowings	296,574	290,854
Subordinated debt and junior subordinated debt	144,410	174,448
Other liabilities - interest rate derivatives	14,774	5,081
Accrued interest payable	$ 6,559	$ 4,627