Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 34,343	$ 28,778	$ 106,322	$ 88,090
Other comprehensive (loss) income, net of tax
Unrealized (losses) gains on securities	3,823	(928)	4,001	13,079
Pension and other postretirement benefits	1,110	455	3,330	1,367
Other comprehensive (loss) income, net of tax	4,933	(473)	7,331	14,446
Comprehensive income	$ 39,276	$ 28,305	$ 113,653	$ 102,536