Income Taxes Deferred income tax assets (liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets and liabilities [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	$ 2,749	$ 0
Non-current deferred tax asset	46,135	33,670
Deferred Tax Assets, Net	23,288	20,565
Non-current deferred tax asset, gross total [Member]
Deferred tax assets and liabilities [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Foreign	0	1,223
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Other	8,368	857
Noncurrent deferred tax asset - acquired future tax deductions	10,580	6,473
Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost	8,633	11,089
Deferred Tax Assets, Unrealized Currency Losses	3,425	5,175
Noncurrent deferred tax asset - tax credits state	8,471	6,764
Deferred Tax Assets, Inventory	10,658	1,938
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts	636	151
Deferred Tax Assets, Valuation Allowance, Noncurrent	(7,385)	0
Noncurrent deferred tax liability [Member]
Deferred tax assets and liabilities [Line Items]
Noncurrent deferred tax liability - depreciation and amortization	21,005	10,027
Noncurrent deferred tax liability - state income taxes	1,640	1,708
Noncurrent deferred tax liability - foreign	202	1,370
Deferred Tax Liabilities, Net	$ 22,847	$ 13,105