Income Taxes - Other Income Tax Disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Uncertain tax positions
Tax reserves related to current year uncertain tax positions	$ 3,600
Tax reserves related to prior year uncertain tax positions	3,100
Net tax expense in connection with uncertain tax positions	8,000
Unrecognized tax benefits	30,950	$ 26,792	$ 2,198
Tax positions that, if reversed, would affect the effective tax rate	25,100	9,400
Currency translation gains	100	1,700
Interest and penalties recognized, net of deferred taxes	1,700	300
Reductions in previously accrued interest and penalties	100
Previously recorded accrued interest for uncertain tax positions that have settled and/or closed	1,400
Prepaid Taxes	12,000	$ 30,100
Income tax refund received	28,100
Noncurrent tax liabilities
Uncertain tax positions
Unrecognized tax benefits	31,800
U.S.
Uncertain tax positions
Proceeds from income tax settlement	9,500
Canadian Revenue Agency
Uncertain tax positions
Proceeds from income tax settlement	$ 29,700