Other Comprehensive Income (Loss) - Other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Other comprehensive income (loss), before tax amount
Other comprehensive income (loss), before tax amount	$ 6,367	$ (67,291)
Other comprehensive income (loss), tax (expense) benefit
Other comprehensive income (loss), tax (expense) benefit	(2,264)	24,917
Other comprehensive income (loss):
Other comprehensive income (loss), net of tax	4,103	(42,374)
Foreign Currency Translation Adjustment
Other comprehensive income (loss), before tax amount
Other comprehensive income (loss), before reclassifications, before tax	207
Other comprehensive income (loss):
Other comprehensive income (loss), before reclassifications, net of tax	207
Unrealized/Recognized Gains (Losses)
Other comprehensive income (loss), before tax amount
Other comprehensive income (loss), before reclassifications, before tax	6,164	(2,601)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(4)	(64,690)
Other comprehensive income (loss), tax (expense) benefit
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(2,265)	963
Amounts reclassified from accumulated other comprehensive income (loss), tax (expense) benefit	1	23,954
Other comprehensive income (loss):
Other comprehensive income (loss), before reclassifications, net of tax	3,899	(1,638)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	$ (3)	$ (40,736)