Debt (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended		1 Months Ended
	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2010	Dec. 18, 2014
Debt Instrument [Line Items]
Material pledge percentage	65.00%			65.00%
Bank, legal and other fees	$ 8.3			$ 8.3	$ 8.1
Fees capitalized and amortized into interest expense	7.2			7.2
Maximum unrestricted cash and cash equivalents for leverage ratio calculation		100
Required prepayment amount, percent of consolidated excess cash flow		50.00%
Required prepayment amount below leverage ratio, percent of consolidated excess cash flow		0.00%
Credit facility, covenant leverage ratio threshold		3.5
Unamortized debt financing costs written off	18.9
Subordinated notes payable		103.1	104.1
Senior Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity					1,050.0
Basis spread on LIBOR			3.00%
Amended Senior Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity					1,300.0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		250.0			250.0
Amount outstanding		0
Credit facility, remaining borrowing capacity		242.2
Letters of Credit [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		150.0			150.0
Letters of credit, amount outstanding		7.8
Term Loan A [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity					250.0
Term Loan B [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity					800.0
Subordinated Debt [Member]
Debt Instrument [Line Items]
Amount outstanding		0
Letters of credit, amount outstanding		59.3
Amended Senior Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	1,300.0			1,300.0
Additions to credit facility					250
Basis spread on LIBOR				2.50%
Amended Senior Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	250.0			250.0
Amended Senior Credit Facility [Member] | Letters of Credit [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	150.0			150.0
Amended Senior Credit Facility [Member] | Term Loan A [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	550.0			550.0
Maturity date		Mar. 01, 2018
Amended Senior Credit Facility [Member] | Term Loan B [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	475.0			475.0
Maturity date		Mar. 01, 2020
Securitization Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	75.0	90.0		75.0		100.0
Credit facility, maximum borrowing capacity March through September							100
Credit facility, maximum borrowing capacity October through February							90
Maturity date		Dec. 01, 2017		Mar. 01, 2016		Dec. 01, 2014
Securitization Facility [Member] | Letters of Credit [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		75.5
Amount outstanding		59.3
Letters of credit, amount outstanding		16.2
Securitization Facility [Member] | ARC [Member]
Debt Instrument [Line Items]
Ownership interest		100.00%
International Subsidiary Letters Of Credit [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		5.0
Amount outstanding		0
Credit facility, remaining borrowing capacity		4.8
International Subsidiary Letters Of Credit [Member] | Letters of Credit [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity		0.3
Amount outstanding		0.2
Credit facility, remaining borrowing capacity		0.1
International Subsidiary Letters Of Credit [Member] | Subordinated Debt [Member]
Debt Instrument [Line Items]
Letters of credit, amount outstanding		$ 0.2