CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 56,618	$ 822,852	$ 235,030	$ 1,069,582
Other comprehensive (loss) income, net of tax:
Change in unrealized investment gains and losses (note 7)	(14,434)	95,295	92,731	51,212
Benefit plan adjustments	(241)	(7,355)	(722)	(8,447)
Foreign currency translation adjustment	(10)	(2,947)	(974)	(4,571)
Other comprehensive (loss) income, net of tax	(14,685)	84,993	91,035	38,194
Comprehensive income	$ 41,933	$ 907,845	$ 326,065	$ 1,107,776