Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income	$ 20,044	$ 12,214
Other comprehensive income (loss), before tax:
Change in net unrealized gains (losses) during period	(5,717)	755
Reclassification adjustment for net gains included in income	(8)	(31)
Defined benefit post-retirement benefits plans:
Change in net actuarial loss	35	33
Other comprehensive income (loss), before tax	(5,690)	757
Deferred tax benefit (expense) related to other comprehensive income	2,239	(297)
Other comprehensive income (loss), net of tax	(3,451)	460
Comprehensive income, net of tax	$ 16,593	$ 12,674