Other Comprehensive Income (Loss) - Other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other comprehensive income (loss), before tax amount
Other comprehensive income (loss), before tax amount	$ 725	$ (2,732)	$ 7,902	$ (96,479)
Other comprehensive income (loss), tax (expense) benefit
Other comprehensive income (loss), tax (expense) benefit	(183)	999	(2,509)	35,155
Other comprehensive income (loss):
Total other comprehensive income (loss), net of tax	542	(1,733)	5,393	(61,324)
Foreign Currency Translation Adjustment
Other comprehensive income (loss), before tax amount
Other comprehensive income (loss), before reclassifications, before tax	232		1,078
Other comprehensive income (loss):
Other comprehensive income (loss), before reclassifications, net of tax	232		1,078
Unrealized/Recognized Gains (Losses)
Other comprehensive income (loss), before tax amount
Other comprehensive income (loss), before reclassifications, before tax	494	102	7,459	(2)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(1)	(2,834)	(635)	(96,477)
Other comprehensive income (loss), tax (expense) benefit
Other comprehensive income (loss), before reclassifications, tax (expense) benefit	(183)	(37)	(2,743)	1
Amounts reclassified from accumulated other comprehensive income (loss), tax (expense) benefit		1,036	234	35,154
Other comprehensive income (loss):
Other comprehensive income (loss), before reclassifications, net of tax	311	65	4,716	(1)
Amounts reclassified from accumulated other comprehensive income (loss), net of tax	$ (1)	$ (1,798)	$ (401)	$ (61,323)