Debt (Revolving Credit Facility) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2014	Dec. 31, 2015	Mar. 03, 2014	Mar. 11, 2013
Secured Debt, Current	$ 40.0		$ 60.0
Proceeds from (Repayments of) Debt		$ 344.9
Debt Instrument, Unamortized Discount			5.1
Debt Instrument, Interest Rate, Basis for Effective Rate	0.026
Credit facility, amount outstanding	$ 212.2		$ 212.0
2014 Credit Facility [Member]
Line of credit, maximum borrowing capacity				$ 650.0
2011 Credit Facility [Member]
Line of credit, maximum borrowing capacity					$ 300.0
2014 Term Loan [Member]
Line of credit, maximum borrowing capacity				350.0
Credit facility, amount outstanding	215.0
2014 Revolving Credit Facility [Member]
Line of credit, maximum borrowing capacity	$ 300.0			$ 300.0