Long-Term Debt Revolving Credit Facility and Term Facility (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Write off of Deferred Debt Issuance Cost	$ 0.5
Payments of Debt Issuance Costs		$ 0.0	$ 0.3	$ 16.7
Line of Credit Facility, Interest Rate Description		Borrowings under the revolving credit facility and term facility bear interest at rates based on adjusted LIBOR or an alternate base rate, plus an applicable margin. The applicable margin for LIBOR-based loans will be between 1.5% and 3.0%.
Line of credit facility, reduction in borrowing capacity, termination of loan facility	$ 72.8
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 523.5
Line of Credit Facility, Remaining Borrowing Capacity		513.1
Letters of Credit Outstanding, Amount		10.4
Loans Payable [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		150.0
Debt Instrument, Periodic Payment, Principal		142.5
Write off of Deferred Debt Issuance Cost		0.8
Payments of Debt Issuance Costs			$ 0.1	$ 6.9
Loans Payable [Member] | Voluntary Prepayment of Term Loan Principal [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Periodic Payment, Principal		135.9
Loans Payable [Member] | Voluntary Prepayment of Term Loan Principal - Due in 2015 [Member] [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Periodic Payment, Principal		$ 2.8