Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2012
Other comprehensive income (loss), before tax amount
Other comprehensive income (loss), before tax amount	$ (2,732)	$ (15,907)	$ (96,479)	$ (62,877)
Other comprehensive income (loss), tax (expense) benefit
Other comprehensive income (loss), tax (expense) benefit	999	5,942	35,155	(39,430)
Other comprehensive income (loss):
Other comprehensive income (loss), net of tax	(1,733)	(9,965)	(61,324)	(102,307)
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	102	(15,829)	(2)	30,998
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(2,834)	(78)	(96,477)	(93,875)
Other comprehensive income (loss), tax (expense) benefit
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(37)	5,913	1	(11,451)
Amounts reclassified from accumulated other comprehensive income (loss), tax (expense) benefit	1,036	29	35,154	(27,979)
Other comprehensive income (loss):
Other comprehensive income (loss), before reclassifications, net of tax	65	(9,916)	(1)	19,547
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	$ (1,798)	$ (49)	$ (61,323)	$ (121,854)