Fair Value - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Equity securities	$ 6,842	$ 5,582
Investment securities available-for-sale	5,385,091	4,123,416
Derivative assets	51,301	29,005
Derivative liabilities	12,393	12,550
U.S. Treasury [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	17,682	5,301
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	592,984	628,151
Mortgage-Backed Securities - Agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	3,183,861	2,209,295
States and Political Subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	1,275,643	940,429
Pooled Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	8,222	8,495
Other Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	306,699	331,745
Fair Value on Recurring Basis [Member] \| Carrying Value [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Equity securities	6,842	5,582
Residential loans held for sale	46,898	14,911
Derivative assets	51,301	29,005
Derivative liabilities	12,393	12,550
Fair Value on Recurring Basis [Member] \| Carrying Value [Member] \| U.S. Treasury [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	17,682	5,301
Fair Value on Recurring Basis [Member] \| 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	592,984	628,151
Fair Value on Recurring Basis [Member] \| 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	3,183,861	2,209,295
Fair Value on Recurring Basis [Member] \| 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	1,275,643	940,429
Fair Value on Recurring Basis [Member] \| 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	8,222	8,495
Fair Value on Recurring Basis [Member] \| Carrying Value [Member] \| Other Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	306,699	331,745
Fair Value on Recurring Basis [Member] \| 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]
Equity securities	6,842	5,582
Fair Value on Recurring Basis [Member] \| 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	46,898	14,911
Derivative assets	51,301	29,005
Derivative liabilities	12,393	12,550
Fair Value on Recurring Basis [Member] \| 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	17,682	5,301
Fair Value on Recurring Basis [Member] \| 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	592,984	628,151
Fair Value on Recurring Basis [Member] \| 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	3,183,861	2,209,295
Fair Value on Recurring Basis [Member] \| 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	1,275,603	936,321
Fair Value on Recurring Basis [Member] \| Estimate of Fair Value Measurement [Member] \| States and Political Subdivisions [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investment securities available-for-sale	40	4,108
Fair Value on Recurring Basis [Member] \| 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	8,222	8,495
Fair Value on Recurring Basis [Member] \| 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	31,169	30,259
Fair Value on Recurring Basis [Member] \| 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	$ 275,530	$ 301,486

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Fair value portion of mortgage loans held-for-sale.

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