Convertible Senior Notes - Narrative (Details)		3 Months Ended	6 Months Ended
	Apr. 15, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($) trading_day	Jun. 30, 2019 USD ($) business_day
Debt Instrument [Line Items]
Implied estimated effective rate	10.24%
Issuance cost, equity component		$ 1,100,000	$ 1,100,000	$ 1,100,000	$ 1,100,000	$ 1,100,000
Description of event of default, default on payment of interest period	30 days
Description of event of default, aggregate principal amount of final judgments	$ 10,000,000
Description of event of default, final judgment payment period	60 days
Percentage of principal amount due if event of default occurs (at least)	25.00%
Income tax benefit, equity transaction		0	4,100,000
Convertible Senior Notes due 2024 | Convertible Notes
Debt Instrument [Line Items]
Debt issued	$ 80,000,000.0	80,000,000	80,000,000	$ 80,000,000	$ 80,000,000	$ 80,000,000
Stated interest rate	4.50%
Conversion rate	0.0350217
Convertible debt, threshold, trading days | trading_day					20
Convertible debt, threshold, consecutive trading days | trading_day					30
Convertible debt, threshold percentage				130.00%
Convertible debt, measurement period					5	5
Convertible debt, measurement period percentage				98.00%
Liability, debt	$ 62,400,000
Equity component of notes	$ 17,600,000	17,624,000	17,624,000	$ 17,624,000	$ 17,624,000	$ 17,624,000
Induced conversion of convertible debt expense		600,000
Issuance costs		4,900,000	4,900,000	4,900,000	4,900,000	4,900,000
Issuance cost, equity component		1,094,000	1,094,000	1,094,000	1,094,000	1,094,000
Issuance cost, debt		$ 3,800,000	$ 3,800,000	$ 3,800,000	$ 3,800,000	$ 3,800,000