Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Consolidated Statements of Comprehensive Income
Net income	$ 245,536	$ 313,331	$ 252,998
Other comprehensive income:
Unrealized appreciation (depreciation) of available for sale investment securities during the year, net of income tax expense (benefit) of $2, $1 and $(9), respectively	(4,771)	(6,158)	2,105
Pension and postretirement benefits, net of income tax expense (benefit) of $(3,794), $(16,725) and $17,272, respectively	(6,291)	(28,426)	28,833
Comprehensive income	$ 234,474	$ 278,747	$ 283,936