Debt - 2019 Capped Call Transactions (Details) - Convertible Debt - Capped Call Transaction - USD ($) $ / shares in Units, $ in Millions			1 Months Ended
	Sep. 18, 2019	Mar. 08, 2018	Sep. 30, 2019	Mar. 31, 2018
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior notes			$ 76.2	$ 34.2
Transaction price cap (in dollars per share)			$ 148.63	$ 52.76
Cap premium percentage over reported sales price	150.00%	100.00%