Convertible Debt and Notes Payable - Convertible Debt (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 14, 2017
Debt and Capital Lease Obligations [Line Items]
Purchase of treasury stock, cost				$ 43,400,000
Convertible debt	[1]	$ 122,485,000		122,485,000		$ 118,688,000
Amortization of debt discount				3,393,000	$ 3,511,000
Convertible Debt
Debt and Capital Lease Obligations [Line Items]
Convertible debt		122,485,000		122,485,000
Convertible debt, unamortized discount		11,400,000		11,400,000		$ 14,900,000
2022 convertible note | Convertible Debt
Debt and Capital Lease Obligations [Line Items]
Debt Instrument, Face Amount							$ 135,000,000.0
Debt Instrument, Convertible, Conversion Price							$ 17.375
Convertible debt		135,000,000.0		135,000,000.0
Interest on Convertible Debt, Net of Tax		1,000,000.0	$ 1,000,000.0	3,000,000.0	3,000,000.0
Convertible debt, unamortized discount							$ 23,400,000
Amortization of debt discount		$ 1,200,000	$ 1,100,000	$ 3,500,000	$ 3,200,000
Debt Instrument, Interest Rate, Effective Percentage							7.13%
Debt Issuance Costs, Gross							$ 2,200,000

[1] The carrying amount of the convertible debt includes an unamortized discount of $11.4 million and $14.9 million as of September 30, 2020 and December 31, 2019, respectively.