Summary of Significant Accounting Policies - Impact of New Accounting Standards ASC 606 on Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Cash flows (used in) provided by operating activities:
Net (loss) income	$ 1,291	$ 21,417	$ (14,048)	$ 39,193
Deferred income taxes			(5,379)	(10,253)
Changes in operating assets and liabilities:
Accounts receivable			24,225	47,265
Inventory			(23,075)	3,079
Prepaid expenses and other assets			(1,859)	(452)
Prepaid income taxes			(28)	463
Accrued expenses and other current liabilities			(6,387)	(5,113)
Deferred revenue			(5,380)	(2,282)
Net cash (used in) provided by operating activities			(31,120)	$ 82,368
Accounting Standards Update 2014-09 | Adjustments
Cash flows (used in) provided by operating activities:
Net (loss) income	(484)		(480)
Deferred income taxes			190
Changes in operating assets and liabilities:
Accounts receivable			75
Inventory			120
Prepaid expenses and other assets			(121)
Prepaid income taxes			(330)
Accrued expenses and other current liabilities			362
Deferred revenue			184
Accounting Standards Update 2014-09 | Without adoption of ASC 606
Cash flows (used in) provided by operating activities:
Net (loss) income	$ 807		(14,528)
Deferred income taxes			(5,189)
Changes in operating assets and liabilities:
Accounts receivable			24,300
Inventory			(22,955)
Prepaid expenses and other assets			(1,980)
Prepaid income taxes			(358)
Accrued expenses and other current liabilities			(6,025)
Deferred revenue			(5,196)
Net cash (used in) provided by operating activities			$ (31,120)