Senior Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Covenants [Abstract]
Covenant limitation incur additional debt in excess of	$ 250,000,000
Maximum pro forma senior leverage ratio	2.50
Pro forma consolidated leverage ratio	2.75
Consolidated funded debt outstanding	651,400,000
Consolidated EBITDA	397,700,000
Outstanding indebtedness less cash in excess of	25,000,000
Adjusted Consolidated EBITDA	553,400,000
Consolidated fixed charges	329,700,000
Debt Instrument [Line Items]
Term loan, maximum facility	250,000,000	250,000,000
Term loan, amount outstanding	212,500,000	237,500,000
Term loan, amount available	0	0
Senior credit facilities, maximum facility	750,000,000	750,000,000
Senior credit facilities, amount outstanding	387,500,000	422,500,000
Senior credit facilities, amount available	215,405,000	198,805,000
Debt facilities, maximum facility	770,000,000	770,000,000
Debt facilities, amount outstanding	387,500,000	440,675,000
Debt facilities, amount available	235,405,000	200,630,000
Letters of credit, outstanding	109,600,000	116,200,000
Financial Covenants Ratios (Table Details) [Abstract]
Required consolidated leverage ratio, maximum	3.25
Actual consolidated leverage ratio	1.64
Required fixed charge coverage ratio, minimum	1.35
Actual fixed charge coverage ratio	1.68
Interest Rate [Abstract]
Interest accrued at prime rate plus %, minimum	0.50%
Interest accrued at prime rate plus %, maximum	1.50%
Interest accrued at Eurodollar rate plus %, minimum	1.50%
Interest accrued at Eurodollar rate plus %, maximum	2.50%
Interest period	Interest periods range from seven days (for borrowings under the revolving credit facility only) to one, two, three or six months, at our election
Margin on Eurodollar rate	1.75%
Margin on prime rate	0.75%
Commitment fee percentage, minimum	0.30%
Commitment fee percentage, maximum	0.50%
Schedule Maturity Dates (Table Details) [Abstract]
2013	25,000,000
2014	25,000,000
2015	25,000,000
2016	312,500,000
Total	387,500,000	440,675,000
Senior Debt (Details) [Abstract]
Event of default-3rd party ownership % of our voting stock	35.00%
Event of default-not satisfied or bonded judgment in excess of	50,000,000
Maximum period allowed for pending judgment to satisfy or bond (in days)	30
Maximum fund drawn on individual occasion	100,000,000
Maximum total amount outstanding	221,000,000
Credit Facility Term Loan [Member]
Debt Instrument [Line Items]
Maturity date	Jul. 14, 2016
Credit Facility Revolver [Member]
Debt Instrument [Line Items]
Maturity date	Jul. 14, 2016
Line of credit, maximum facility	500,000,000	500,000,000
Line of credit, amount outstanding	175,000,000	185,000,000
Line of credit, amount available	215,405,000	198,805,000
Intrust Bank Line of Credit [Member]
Debt Instrument [Line Items]
Line of credit, maximum facility	20,000,000	20,000,000
Line of credit, amount outstanding	0	18,175,000
Line of credit, amount available	$ 20,000,000	$ 1,825,000