SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves balance, beginning of year	$ 41,911	$ 14,266	$ 5,587
Deductions	173,569	141,493	61,033
Valuation allowances and reserves balance, end of year	28,542	41,911	14,266
Change in Tax Valuation Allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves balance, beginning of year	15,250	14,309	10,970
Charged to Costs and Expenses	(61)	0	0
Charged other Accounts	(1,880)	941	3,339
Deductions	0	0	0
Valuation allowances and reserves balance, end of year	13,309	15,250	14,309
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves balance, beginning of year	417	90	16
Charged to Costs and Expenses	1,768	347	74
Charged other Accounts		0	0
Deductions	0	20	0
Valuation allowances and reserves balance, end of year	2,185	417	90
Reserve for Inventory Obsolescence
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves balance, beginning of year	410	121	212
Charged to Costs and Expenses	2,000	872	51
Charged other Accounts	9	0	(8)
Deductions	1,115	583	134
Valuation allowances and reserves balance, end of year	$ 1,304	$ 410	$ 121