Debt - Cash Convertible Senior Notes Due 2019 (Details) - USD ($)	1 Months Ended
	Jul. 31, 2017	Jul. 31, 2014	Jun. 30, 2014	Sep. 30, 2019	Jun. 15, 2019
2024 Convertible Notes
Debt Instrument [Line Items]
Stated interest rate	2.875%
Convertible senior notes issued and settled	$ 34,400,000
2.125% Cash Convertible Senior Notes Due 2019
Debt Instrument [Line Items]
Stated interest rate			2.125%	2.125%
Convertible senior notes issued and settled		$ 30,000,000	$ 200,000,000
Amount of retired debt	$ 35,000,000.0
Repurchased amount					$ 195,000,000.0