Income Taxes - Cumulative Tax Effects of Primary Differences (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
Allowance for credit losses	$ 36,419	$ 38,021
OREO writedowns	7,865	11,448
Deferred tax assets operating loss carry-forwards, total	14,886	20,245
Stock based compensation	5,477	5,594
Nonaccrual interest	3,841	3,050
Credit carryforwards	2,509	2,509
Unrealized loss on available for sale securities		2,448
Capital loss carryforwards	8,107	7,724
Other	7,632	2,519
Total gross deferred tax assets	86,736	93,558
Deferred tax asset valuation allowance	(7,980)	(7,596)
Total deferred tax assets	78,756	85,962
Deferred tax liabilities:
Core deposit intangible	(2,465)	(3,069)
Premises and equipment	(2,287)	(4,873)
Deferred loan costs	(3,514)	(2,421)
FHLB dividend	(1,941)	(1,948)
Unrealized gains on financial instruments measured at fair value	(11,535)	(11,326)
Unrealized gain on available for sale securities	(4,686)
Other	(571)	(601)
Total deferred tax liabilities	(26,999)	(24,238)
Net deferred tax asset	$ 51,757	$ 61,724