Senior Debt (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Term loan, maximum facility		$ 225,000,000	$ 250,000,000
Term loan, amount outstanding		223,313,000	187,500,000
Term loan, amount available		0	0
Senior credit facilities, maximum facility		900,000,000	750,000,000
Senior credit facilities, amount outstanding		478,313,000	348,000,000
Senior credit facilities, amount available		315,600,000	234,830,000
Debt facilities, maximum facility		920,000,000	770,000,000
Debt facilities, amount outstanding		492,813,000	366,275,000
Debt facilities, amount available		321,100,000	236,555,000
Letters of credit, amount outstanding		104,400,000	104,700,000
Line of Credit Facility, Interest Rate Description		Borrowings under the Revolving Facility bear interest at varying rates
Commitment fee percentage		0.50%
Senior Credit Facilities, Additional Amount Allowed		250,000,000
Covenants for senior credit facilities - amount available under restricted payment basket		83,000,000
Schedule Maturity Dates (Table Details) [Abstract]
2015		16,750,000
2016		2,250,000
2017		2,250,000
2018		2,250,000
2019		257,250,000
Thereafter		212,063,000
Total		492,813,000	366,275,000
Borrowing in Term Loans	225,000,000
Borrowing in Revolving Debt	100,000,000
Term Loan, Frequency of Periodic Payment		quarterly
Term Loan, Periodic Payment, Principal		562,500
Event of default - 3rd party ownership % of our voting stock		35.00%
Event of default - judgment not satisfied or bonded pending appeal		50,000,000
Event of default - maximum period allowed for pending judgment		30
Financial Covenants Ratios (Table Details) [Abstract]
Required consolidated leverage ratio, maximum		4.50
Actual consolidated leverage ratio		3.56
Required Consolidated Senior Secured Leverage Ratio, Maximum		2.75
Actual Consolidated Senior Secured Leverage Ratio		1.59
Required Consolidated Fixed Charge Coverage Ratio, Minimum		1.50
Actual fixed charge coverage ratio		1.82
Covenants [Abstract]
Consolidated funded debt outstanding		1,021,700,000
Consolidated EBITDA		287,100,000
Covenant limitation incur additional debt in excess of		25,000,000
Consolidated senior secured debt outstanding		457,200,000
Adjusted Consolidated EBITDA		531,400,000
Consolidated fixed charges		291,200,000
Minimum [Member]
Debt Instrument [Line Items]
Commitment fee percentage		0.30%
Maximum [Member]
Debt Instrument [Line Items]
Commitment fee percentage		0.50%
Eurodollar Rate [Member]
Debt Instrument [Line Items]
Description of variable rate basis		Eurodollar
Eurodollar Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Basis margin on variable rate		1.50%
Eurodollar Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Basis margin on variable rate		2.75%
Prime Rate [Member]
Debt Instrument [Line Items]
Description of variable rate basis		prime
Prime Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Basis margin on variable rate		0.50%
Prime Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Basis margin on variable rate		1.75%
Term Loan [Member]
Debt Instrument [Line Items]
Maturity date		Mar. 19, 2021
Term loan, amount outstanding		223,313,000
Margin on Eurodollar rate, actual		3.00%
Margin on ABR rate, actual		2.00%
Schedule Maturity Dates (Table Details) [Abstract]
2015		2,250,000
2016		2,250,000
2017		2,250,000
2018		2,250,000
2019		2,250,000
Thereafter		212,063,000
Revolving Facility [Member]
Debt Instrument [Line Items]
Maturity date		Mar. 19, 2019
Line of credit, maximum facility		675,000,000	500,000,000
Line of credit, amount outstanding		255,000,000	160,500,000
Line of credit, amount available		315,600,000	234,830,000
Senior credit facilities, amount outstanding		255,000,000
Margin on Eurodollar rate, actual		2.50%
Margin on ABR rate, actual		1.50%
Schedule Maturity Dates (Table Details) [Abstract]
2015		0
2016		0
2017		0
2018		0
2019		255,000,000
Thereafter		0
Line of Credit [Member]
Debt Instrument [Line Items]
Maturity date		Aug. 21, 2015
Line of credit, maximum facility		20,000,000	20,000,000
Line of credit, amount outstanding		14,500,000	18,275,000
Line of credit, amount available		5,500,000	1,725,000
Schedule Maturity Dates (Table Details) [Abstract]
2015		14,500,000
2016		0
2017		0
2018		0
2019		0
Thereafter		$ 0