Senior Credit Facilities (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Covenants [Abstract]
Covenant limitation incur additional debt in excess of	$ 250,000,000	$ 250,000,000
Maximum pro forma senior leverage ratio	2.50	2.50
Consolidated fixed charges		342,300,000
Consolidated funded debt outstanding	804,900,000	804,900,000
Consolidated EBITDA		371,100,000
Outstanding indebtedness less cash in excess of	25,000,000	25,000,000
Adjusted Consolidated EBITDA		524,100,000
Pro forma consolidated leverage ratio	2.75	2.75
Financial Covenants Ratios (Table Details) [Abstract]
Required consolidated leverage ratio, maximum	3.25	3.25
Actual consolidated leverage ratio	2.17	2.17
Required fixed charge coverage ratio, minimum	1.35	1.35
Actual fixed charge coverage ratio	1.53	1.53
Interest Rate [Abstract]
Interest accrued at Prime rate plue %, minimum	0.50%	0.50%
Interest accrued at Prime rate plus %, maximum	1.50%	1.50%
Interest accrued at Eurodollar rate plus %, minimum	1.50%	1.50%
Interest accrued at Eurodollar rate plus %, maximum	2.50%	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	2.25%	2.25%
Margin on prime rate	1.25%	1.25%
Commitment fee percentage, minimum	0.30%
Commitment fee percentage, maximum	0.50%
Senior Credit Facilities (Details) [Abstract]
Event of default-3rd party ownership % of our voting stock	35.00%	35.00%
Event of default-not satisfied or bonded judgment in excess of	50,000,000	50,000,000
Maximum period allowed for pending judgment to satisfy or bond (in days)	30	30
Maximum fund drawn on individual occasion	100,000,000	100,000,000
Maximum total amount outstanding	221,000,000	221,000,000
Debt Instrument [Line Items]
Senior credit facilities, maximum amount	750,000,000	750,000,000
Term loan, maximum facility	250,000,000	250,000,000
Term loan, amount outstanding	193,800,000	193,800,000	212,500,000
Line of credit, maximum facility	500,000,000	500,000,000
Line of credit, amount outstanding	89,000,000	89,000,000	175,000,000
Letters of Credit Outstanding, Amount	115,100,000	115,100,000
Letters of credit, amount available	295,900,000	295,900,000
Unsecured line of credit, maximum facility	20,000,000	20,000,000
Unsecured line of credit, amount outstanding	$ 1,800,000	$ 1,800,000	$ 0