Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 12,725	$ 10,908	$ 29,636	$ 20,648
Net change in unrealized gains (losses) on investment securities available-for-sale:
Net Unrealized gains (losses) arising during the period, net of tax expense (benefit) of $5,932, ($11,840), $11,536 and ($14,738), respectively	9,678	(19,316)	18,824	(24,143)
Less: reclassification adjustment for net losses (gains) on sales realized in net income, net of tax (benefit) expense of $139, $344, $358 and $969, respectively	(226)	(562)	(585)	(1,581)
Net change in unrealized gains (losses) on investment securities available-for-sale	9,452	(19,878)	18,239	(25,724)
Net change in unfunded pension liability:
Change in unfunded pension liability related to unrealized loss, prior service cost and transition obligation, net of tax expense of $36, $0, $36 and $0, respectively	60		60
Total other comprehensive (loss) income	9,512	(19,878)	18,299	(25,724)
Total comprehensive income (loss)	$ 22,237	$ (8,970)	$ 47,935	$ (5,076)