Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net income	$ 12,214	$ 9,506
Other comprehensive income, before tax:
Change in net unrealized gain during period	755	417
Reclassification adjustment for gains included in income	(31)	(2)
Defined benefit post-retirement benefits plans:
Change in net actuarial loss	33	35
Other comprehensive income, before tax	757	450
Deferred tax expense related to other comprehensive income	297	177
Other comprehensive income, net of tax	460	273
Comprehensive income, net of tax	$ 12,674	$ 9,779