Income Taxes - Summary of Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation Allowance
Valuation allowance at beginning of year	$ 215,582	$ 256,165	$ 190,174
Mergers and acquisitions, net	418	0	(1,416)
Current year operations	122,853	26,619	67,549
Adoption of new accounting pronouncements	(7,477)	17,843	0
Provisional impact of the Tax Act	0	(87,473)	0
Equity component of long-term debt	(13,367)	0	0
Change in deferred state tax rate	(8,666)	0	0
Changes in foreign tax rates and foreign tax reforms	0	1,327	0
Foreign currency translation adjustment	(1,230)	1,101	(142)
Valuation allowance at end of year	$ 308,113	$ 215,582	$ 256,165