Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net income	$ 67,177	$ 81,127	$ 87,888
Other comprehensive (loss) income:
(Decrease) increase in net unrealized gains on securities available for sale	(17,855)	5,557	19,282
Deferred tax benefit (expense)	7,507	(2,337)	(8,108)
(Decrease) increase in net unrealized gains on securities available for sale, net of tax	(10,348)	3,220	11,174
Post-retirement benefit transition obligation amortization	61	61	61
Deferred tax expense	(25)	(25)	(25)
Post-retirement benefit transition obligation amortization, net of tax	36	36	36
Total other comprehensive (loss) income	(10,312)	3,256	11,210
Total comprehensive income	$ 56,865	$ 84,383	$ 99,098