Revenue - Cumulative Effects Made to the Balance Sheet for ASC 606 Adoption (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017
Assets
Inventories, net	$ 105,614	$ 112,392	$ 95,957	$ 91,689	$ 81,565	$ 86,724	$ 113,074	$ 103,335	$ 97,286
Prepaid expenses and other current assets	22,917	26,905	26,644	20,555	20,525	14,359	14,536	12,453	15,291
Liabilities and Stockholders' Equity
Other accrued liabilities	45,700	44,762	41,884	38,697	33,626	34,332	37,295	30,110	28,809
Accumulated deficit	(135,160)	$ (125,262)	$ (106,443)	$ (94,638)	(80,434)	(82,147)	$ (76,018)	$ (66,817)	$ (59,070)
Adjustments due to ASC 606 | ASC 606
Assets
Inventories, net	(4,586)				(5,159)
Prepaid expenses and other current assets	2,926				6,166
Liabilities and Stockholders' Equity
Other accrued liabilities	(1,952)				(706)
Accumulated deficit	292				$ 1,713
ASC 605
Assets
Inventories, net	110,200					86,724
Prepaid expenses and other current assets	19,991					14,359
Liabilities and Stockholders' Equity
Other accrued liabilities	47,652					34,332
Accumulated deficit	$ (135,452)					$ (82,147)