Fair Value - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	$ 4,838	$ 3,941	$ 3,995
Investment securities available-for-sale	2,648,901	2,418,221	$ 2,572,521
Derivative assets	36,209	15,925
Derivative liabilities	58,040	26,968
U.S. Treasury [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	12,269	12,150
U.S. Government-Sponsored Entities and Agencies [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	540,775	613,550
Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	1,336,605	1,066,361
States and Political Subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	417,163	387,296
Pooled Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	6,720	7,900
Other Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	335,369	330,964
Estimate of Fair Value Measurement [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	4,838	3,941
Estimate of Fair Value Measurement [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Residential loans held for sale	44,422	13,810
Derivative assets	36,209	15,925
Derivative liabilities	58,040	26,968
Estimate of Fair Value Measurement [Member] | U.S. Treasury [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	12,269	12,150
Estimate of Fair Value Measurement [Member] | U.S. Government-Sponsored Entities and Agencies [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	540,775	613,550
Estimate of Fair Value Measurement [Member] | Mortgage-Backed Securities - Agency [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	1,336,605	1,066,361
Estimate of Fair Value Measurement [Member] | States and Political Subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	417,163	387,296
Estimate of Fair Value Measurement [Member] | Pooled Trust Preferred Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	6,720	7,900
Estimate of Fair Value Measurement [Member] | Other Securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	32,139	31,443
Estimate of Fair Value Measurement [Member] | Other Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	303,230	299,521
Carrying Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	4,838	3,941
Residential loans held for sale	44,422	13,810
Derivative assets	36,209	15,925
Derivative liabilities	58,040	26,968
Carrying Value [Member] | U.S. Treasury [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	12,269	12,150
Carrying Value [Member] | U.S. Government-Sponsored Entities and Agencies [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	540,775	613,550
Carrying Value [Member] | Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	1,336,605	1,066,361
Carrying Value [Member] | States and Political Subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	417,163	387,296
Carrying Value [Member] | Pooled Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	6,720	7,900
Carrying Value [Member] | Other Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	$ 335,369	$ 330,964