Disclosures about Fair Value of Financial Instruments - Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring and Nonrecurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	$ 1,160,994	$ 1,248,929
Assets
Assets, Fair Value Disclosure, Nonrecurring	3,421	4,171
Derivative Asset [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	5,160	3,736
Loans Held for Sale - Fair Value Option [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	697,532	747,593
Derivative Liabilities [Member]
Liabilities
Liabilities, Fair Value Disclosure, Recurring	4,346	3,537
Impaired Loans [Member]
Assets
Assets, Fair Value Disclosure, Nonrecurring	2,917	3,836
Other Real Estate Owned [Member]
Assets
Assets, Fair Value Disclosure, Nonrecurring	504	335
Available-for-sale Securities [Member] | Mortgage-backed Securities [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	411,081	451,536
Available-for-sale Securities [Member] | Corporate Notes [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	25,276	25,323
Available-for-sale Securities [Member] | Equity Securities [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	21,945	20,714
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	21,945	20,714
Assets
Assets, Fair Value Disclosure, Nonrecurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Derivative Asset [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Loans Held for Sale - Fair Value Option [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Derivative Liabilities [Member]
Liabilities
Liabilities, Fair Value Disclosure, Recurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Impaired Loans [Member]
Assets
Assets, Fair Value Disclosure, Nonrecurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other Real Estate Owned [Member]
Assets
Assets, Fair Value Disclosure, Nonrecurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Available-for-sale Securities [Member] | Mortgage-backed Securities [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Available-for-sale Securities [Member] | Corporate Notes [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Available-for-sale Securities [Member] | Equity Securities [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	21,945	20,714
Significant Other Observable Inputs (Level 2) [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	1,138,946	1,227,975
Assets
Assets, Fair Value Disclosure, Nonrecurring	0	0
Significant Other Observable Inputs (Level 2) [Member] | Derivative Asset [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	5,057	3,523
Significant Other Observable Inputs (Level 2) [Member] | Loans Held for Sale - Fair Value Option [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	697,532	747,593
Significant Other Observable Inputs (Level 2) [Member] | Derivative Liabilities [Member]
Liabilities
Liabilities, Fair Value Disclosure, Recurring	4,346	3,537
Significant Other Observable Inputs (Level 2) [Member] | Impaired Loans [Member]
Assets
Assets, Fair Value Disclosure, Nonrecurring	0	0
Significant Other Observable Inputs (Level 2) [Member] | Other Real Estate Owned [Member]
Assets
Assets, Fair Value Disclosure, Nonrecurring	0	0
Significant Other Observable Inputs (Level 2) [Member] | Available-for-sale Securities [Member] | Mortgage-backed Securities [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	411,081	451,536
Significant Other Observable Inputs (Level 2) [Member] | Available-for-sale Securities [Member] | Corporate Notes [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	25,276	25,323
Significant Other Observable Inputs (Level 2) [Member] | Available-for-sale Securities [Member] | Equity Securities [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	0	0
Significant Unobservable Inputs (Level 3) [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	103	240
Assets
Assets, Fair Value Disclosure, Nonrecurring	3,421	4,171
Significant Unobservable Inputs (Level 3) [Member] | Derivative Asset [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	103	240
Significant Unobservable Inputs (Level 3) [Member] | Loans Held for Sale - Fair Value Option [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	0	0
Significant Unobservable Inputs (Level 3) [Member] | Derivative Liabilities [Member]
Liabilities
Liabilities, Fair Value Disclosure, Recurring	0	0
Significant Unobservable Inputs (Level 3) [Member] | Impaired Loans [Member]
Assets
Assets, Fair Value Disclosure, Nonrecurring	2,917	3,836
Significant Unobservable Inputs (Level 3) [Member] | Other Real Estate Owned [Member]
Assets
Assets, Fair Value Disclosure, Nonrecurring	504	335
Significant Unobservable Inputs (Level 3) [Member] | Available-for-sale Securities [Member] | Mortgage-backed Securities [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	0	0
Significant Unobservable Inputs (Level 3) [Member] | Available-for-sale Securities [Member] | Corporate Notes [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	0	0
Significant Unobservable Inputs (Level 3) [Member] | Available-for-sale Securities [Member] | Equity Securities [Member]
Available-for-sale securities:
Assets, Fair Value Disclosure, Recurring	$ 0	$ 0