Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2012
Other comprehensive income (loss), before tax amount
Other comprehensive income (loss), before tax amount	$ (26,456)	$ 5,095	$ (93,747)	$ (46,970)
Other comprehensive income (loss), tax (expense) benefit
Other comprehensive income (loss), tax (expense) benefit	9,239	(1,961)	34,156	(45,372)
Other comprehensive income (loss):
Other comprehensive income (loss), net of tax	17,217	3,134	(59,591)	(92,342)
Deferred tax asset valuation allowance released					$ 63,000
Deferred tax asset valuation allowance reclassified from AOCI				63,000
Unrealized/Recognized Gains (Losses)
Other comprehensive income (loss), before tax amount
Other comprehensive income (loss), before reclassifications, before tax	2,497	39,405	(104)	46,827
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(28,953)	(34,310)	(93,643)	(93,797)
Other comprehensive income (loss), tax (expense) benefit
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(916)	(14,490)	38	(17,234)
Amounts reclassified from accumulated other comprehensive income (loss), tax (expense) benefit	10,155	12,529	34,118	(28,138)
Other comprehensive income (loss):
Other comprehensive income (loss), before reclassifications, net of tax	1,581	24,915	(66)	29,593
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	$ (18,798)	$ (21,781)	$ (59,525)	$ (121,935)