Consolidated Statements of Comprehensive Income (unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income	$ 17,271	$ 21,005
Other comprehensive income:
Increase in net unrealized gains on securities available for sale	1,272	1,384
Deferred tax expense	(534)	(582)
Increase in net unrealized gains on securities available for sale, net of tax	738	802
Post-retirement benefit transition obligation amortization	15	15
Deferred tax expense	(6)	(6)
Post-retirement benefit transition obligation amortization, net of tax	9	9
Total other comprehensive income	747	811
Total comprehensive income	$ 18,018	$ 21,816