Long-Term Debt - Convertible Senior Notes (Details) - USD ($)		3 Months Ended		9 Months Ended
	May 01, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	May 05, 2015
Carrying amount of Notes on the balance sheet:
Purchases of Convertible Notes				$ (88,961,000)	$ (33,915,000)
Settlement of Convertible Notes
Carrying amount of Notes on the balance sheet:
Purchases of Convertible Notes	$ (69,200,000)
Senior Notes
Debt Instrument [Line Items]
Stated interest rate							250.00%
Repurchased face amount		$ 89,100,000	$ 34,300,000	89,100,000	34,300,000
Repayments of debt				89,000,000.0	33,900,000
Gain (loss) on extinguishment of debt		0	0	166,000	711,000
Repurchase amount		0	0	0	0
Carrying amount of Notes on the balance sheet:
Convertible senior notes, principal amount		0		0		$ 158,295,000
Unamortized debt discount		0		0		(1,667,000)
Unamortized debt issuance costs		0		0		(330,000)
Convertible senior notes, net		0		0		$ 156,298,000
Contractual coupon interest		0	989,000	1,063,000	3,254,000
Debt discount amortization		0	1,208,000	1,196,000	3,934,000
Amortization of debt issuance costs		0	239,000	236,000	778,000
Interest expense		$ 0	$ 2,436,000	$ 2,662,000	$ 8,677,000
Interest on Convertible Debt, Net of Tax	$ 900,000