Loans - Nonaccrual Loans, Segregated by Loan Class (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	$ 35,866	$ 38,573
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	7,501	2,935
Commercial real estate: Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	16,895	24,008
Residential: 1-4 family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	10,953	11,630
Residential: Home equities [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	$ 517	$ 0