CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 1,172,000	$ 251,949	$ (49,848)
Other comprehensive income (loss), net of tax
Change in unrealized investment gains and losses	40,403	91,139	(123,591)
Benefit plans adjustment	(15,714)	(52,112)	68,038
Foreign currency translation adjustment	(4,228)	(2,642)	(14,010)
Total other comprehensive income, net of tax	20,461	36,385	(69,563)
Comprehensive income (loss)	$ 1,192,461	$ 288,334	$ (119,411)