Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 39,713	$ 30,868	$ 71,979	$ 59,312
Other comprehensive (loss) income, net of tax
Unrealized (losses) gains on securities	(5,365)	6,564	178	14,007
Pension and other postretirement benefits	1,110	456	2,220	912
Other comprehensive (loss) income, net of tax	(4,255)	7,020	2,398	14,919
Comprehensive income	$ 35,458	$ 37,888	$ 74,377	$ 74,231