Recorded Investment in Nonaccrual and Loans Past due 90 Days and Still on Accrual by Class of Loan (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	$ 77,344	$ 101,767
Loans Past Due 90 Day And Over Still Accruing		232
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	2,735	2,886
Commercial Real Estate | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	7,169	8,528
Commercial Real Estate | Farmland
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	6,755	7,844
Commercial Real Estate | Nonfarm nonresidential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	44,771	48,447
Residential Real Estate | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	558	7,513
Residential Real Estate | 1-4 Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	14,872	26,098
Loans Past Due 90 Day And Over Still Accruing		230
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual		9
Loans Past Due 90 Day And Over Still Accruing		2
Agriculture
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	299	322
Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual	$ 185	$ 120