Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net Income	$ 14,426	$ 11,413	$ 39,549	$ 41,049
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 $3,787, $(477), $2,892 and $11,060, respectively	6,178	(778)	4,721	18,046
Less: reclassification adjustment for net gains on sales realized in net income, net of tax expense of ($29), ($13), ($381) and ($371), respectively	(47)	(23)	(623)	(608)
Net change in unrealized (losses) gains on investment securities available-for-sale	6,131	(801)	4,098	17,438
Net change in securities held-to-maturity
Amortization of unrealized gain on securities reclassified to held-to-maturity, net of tax benefit of ($55), $0, ($175), $0, respectively	(104)		(312)
Net change in unfunded pension liability
Change in unfunded pension liability related to unrealized (loss) gain, prior service cost and transition obligation, net of tax (benefit) expense of ($9), $3, ($27) and $39, respectively	(15)	5	(45)	65
Net current-period other comprehensive income (loss)	6,012	(796)	3,741	17,503
Total comprehensive income	$ 20,438	$ 10,617	$ 43,290	$ 58,552