Fair Values of Assets and Liabilities - Schedule of Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	$ (778,612)	$ (886,560)
Assets, Fair Value Disclosure	829,181	966,548
Balance, beginning of period	37,828	30,419
Total gains or losses included in earnings	589	111
Total gains or losses included in other comprehensive income	850	7,608
Purchases	430	750
Issuances	0	0
Sales	0	0
Settlements	(3,805)	(1,060)
Transfers from Level 3	536	0
Transfers into Level 3	536	0
Balance, end of period	35,892	37,828
Federal Home Loan Bank Stock	36,498	62,952
Loans Held-for-sale, Fair Value Disclosure	7,052	5,763
Other Assets, Fair Value Disclosure	7,019	11,273
Other Liabilities, Fair Value Disclosure	5,972	10,829
Financial and Nonfinancial Liabilities, Fair Value Disclosure	5,972	10,829
Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	35,658	28,999
Total gains or losses included in earnings	589	111
Total gains or losses included in other comprehensive income	850	7,608
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	(3,805)	(1,060)
Transfers from Level 3	0	0
Transfers into Level 3	0	0
Balance, end of period	33,292	35,658
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	2,170	1,420
Total gains or losses included in earnings	0	0
Total gains or losses included in other comprehensive income	0	0
Purchases	36	750
Issuances	0	0
Sales	0	0
Settlements	0	0
Transfers from Level 3	536	0
Transfers into Level 3	0	0
Balance, end of period	1,670	2,170
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning of period	0	0
Total gains or losses included in earnings	0	0
Total gains or losses included in other comprehensive income	0	0
Purchases	394	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Transfers from Level 3	0	0
Transfers into Level 3	536	0
Balance, end of period	930	0
Corporate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(6,319)	(2,319)
Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(776,942)	(884,390)
Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(33,292)	(35,658)
US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(16,617)	(22,092)
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(676,853)	(777,577)
Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Commercial [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(1)	(28)
Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(16,631)	(19,118)
Obligations of States and Political Subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(27,229)	(27,598)
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(1,670)	(2,170)
Level 1 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Assets, Fair Value Disclosure	0	0
Federal Home Loan Bank Stock	0	0
Loans Held-for-sale, Fair Value Disclosure	0	0
Other Assets, Fair Value Disclosure	0	0
Other Liabilities, Fair Value Disclosure	0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0
Level 1 [Member] | Corporate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 1 [Member] | Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 1 [Member] | Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 1 [Member] | US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 1 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 1 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Commercial [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 1 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 1 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 1 [Member] | Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(743,650)	(848,732)
Assets, Fair Value Disclosure	793,289	928,720
Federal Home Loan Bank Stock	36,498	62,952
Loans Held-for-sale, Fair Value Disclosure	7,052	5,763
Other Assets, Fair Value Disclosure	6,089	11,273
Other Liabilities, Fair Value Disclosure	5,972	10,829
Financial and Nonfinancial Liabilities, Fair Value Disclosure	5,972	10,829
Level 2 [Member] | Corporate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(6,319)	(2,319)
Level 2 [Member] | Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(743,650)	(848,732)
Level 2 [Member] | Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Level 2 [Member] | US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(16,617)	(22,092)
Level 2 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(676,853)	(777,577)
Level 2 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Commercial [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(1)	(28)
Level 2 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(16,631)	(19,118)
Level 2 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(27,229)	(27,598)
Level 2 [Member] | Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(34,962)	(37,828)
Assets, Fair Value Disclosure	35,892	37,828
Federal Home Loan Bank Stock	0	0
Loans Held-for-sale, Fair Value Disclosure	0	0
Other Assets, Fair Value Disclosure	930	0
Other Liabilities, Fair Value Disclosure	0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, Fair Value Disclosure	33,292
Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, Fair Value Disclosure	1,670
Fair Value, Inputs, Level 3 [Member] | Corporate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Debt Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value		(35,658)
Fair Value, Inputs, Level 3 [Member] | Pooled Trust Preferred Collateralized Debt Obligations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	(33,292)	(35,658)
Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Residential [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Mortgage-Backed Securities-Commercial [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Obligations of U.S. Government-Sponsored Enterprises [Member] | Other Government - Sponsored Enterprises [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Obligations of States and Political Subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value	$ 0	0
Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available for sale, at fair value		$ (2,170)