Debt Commitments - Note Payable Under Asset Purchase Agreement (Details) - USD ($) $ in Millions		1 Months Ended
	Dec. 07, 2015	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2017
Debt Instrument [Line Items]
Consideration for Apex asset purchase agreement	$ 27.0
Cash paid for asset purchase agreement			$ 5.0	$ 5.0	$ 12.0
Debt				390.0		$ 440.0
Note Payable Under Asset Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt				$ 10.0	$ 15.0	$ 5.0
Fixed interest rate per annum						0.56%
Scenario, Forecast [Member]
Debt Instrument [Line Items]
Cash paid for asset purchase agreement		$ 5.0