Debt and Debt Issuance Costs - Convertible Notes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Gain (loss) on repurchase of debt instrument	$ (11,501,000)	$ 0	$ 0
Amortization of debt issuance costs	3,376,000	3,183,000	2,415,000
Net proceeds from sale of the Notes	342,575,000	4,560,000	$ 167,043,000
Convertible Senior Notes
Debt Instrument [Line Items]
Repurchase amount	$ 114,999,000
Shares repurchased and canceled (in shares)	114,997,000
Redemption price (as a percent)	107.50%
Interest paid	$ 1,600,000
Gain (loss) on repurchase of debt instrument	(11,500,000)
Amortization of debt issuance costs	2,300,000
Long-term debt, gross	$ 0	$ 115,000,000
Convertible Senior Notes | 5.00% Convertible Senior Notes due 2021
Debt Instrument [Line Items]
Stated interest rate	5.00%