Long-term Debt - Propco Credit Agreement (Details) (Propco [Member], USD $)	12 Months Ended				12 Months Ended			12 Months Ended			12 Months Ended				12 Months Ended		12 Months Ended												12 Months Ended					12 Months Ended								12 Months Ended			12 Months Ended
	Dec. 31, 2012 Credit Agreement [Member]	Jun. 18, 2011 Credit Agreement [Member] Additional_Extension_Periods	Dec. 31, 2012 Term Loan Facility [Member]	Jun. 18, 2011 Term Loan Facility [Member] Tranches	Dec. 31, 2012 Tranche B-1 [Member]	Dec. 31, 2011 Tranche B-1 [Member]	Jun. 18, 2011 Tranche B-1 [Member]	Dec. 31, 2012 Tranche B-2 [Member]	Dec. 31, 2011 Tranche B-2 [Member]	Jun. 18, 2011 Tranche B-2 [Member]	Dec. 31, 2012 Tranche B-3 [Member]	Jan. 03, 2012 Tranche B-3 [Member]	Dec. 31, 2011 Tranche B-3 [Member]	Jun. 18, 2011 Tranche B-3 [Member]	Dec. 31, 2012 Revolving Credit Facility [Member]	Dec. 31, 2011 Revolving Credit Facility [Member]	Dec. 31, 2012 Minimum [Member] Term Loan Facility [Member]	Dec. 31, 2012 1st Tier [Member] Tranche B-1 [Member]	Dec. 31, 2012 2nd Tier [Member] Tranche B-1 [Member]	Dec. 31, 2012 3rd Tier [Member] Tranche B-1 [Member]	Dec. 31, 2012 Interest Rate Swap [Member] Term Loan Facility [Member]	Jun. 18, 2011 Interest Rate Swap [Member] Term Loan Facility [Member]	Dec. 31, 2012 Minimum [Member] 1st Tier [Member] Tranche B-1 [Member]	Dec. 31, 2012 Minimum [Member] 2nd Tier [Member] Tranche B-1 [Member]	Dec. 31, 2018 Maximum [Member]	Dec. 31, 2012 Maximum [Member]	Dec. 31, 2012 Maximum [Member] 2nd Tier [Member] Tranche B-1 [Member]	Dec. 31, 2012 Maximum [Member] 3rd Tier [Member] Tranche B-1 [Member]	Dec. 31, 2012 LIBOR [Member] Tranche B-1 [Member]	Dec. 31, 2012 LIBOR [Member] Tranche B-2 [Member]	Dec. 31, 2012 LIBOR [Member] Maximum [Member] Tranche B-2 [Member]	Dec. 31, 2012 LIBOR [Member] Maximum [Member] Revolving Credit Facility [Member]	Dec. 31, 2012 LIBOR [Member] Minimum [Member] Tranche B-2 [Member]	Dec. 31, 2012 LIBOR [Member] Interest Rate Swap [Member] Term Loan Facility [Member]	Dec. 31, 2012 LIBOR [Member] Year 1 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 LIBOR [Member] Year 2 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 LIBOR [Member] Year 3 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 LIBOR [Member] Year 4 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 LIBOR [Member] Year 5 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 LIBOR [Member] Year 6 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 LIBOR [Member] Year 7 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 Base Rate [Member] Tranche B-1 [Member]	Dec. 31, 2012 Base Rate [Member] Maximum [Member] Tranche B-2 [Member]	Dec. 31, 2012 Base Rate [Member] Maximum [Member] Revolving Credit Facility [Member]	Dec. 31, 2012 Base Rate [Member] Minimum [Member] Tranche B-1 [Member]	Dec. 31, 2012 Base Rate [Member] Year 1 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 Base Rate [Member] Year 2 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 Base Rate [Member] Year 3 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 Base Rate [Member] Year 4 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 Base Rate [Member] Year 5 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 Base Rate [Member] Year 6 [Member] Maximum [Member] Tranche B-1 [Member]	Dec. 31, 2012 Base Rate [Member] Year 7 [Member] Maximum [Member] Tranche B-1 [Member]
Debt Instrument [Line Items]
Number of debt tranches				3
Long-term debt, aggregate principal amount	$ 931,300,000			$ 1,575,000,000.000			$ 200,000,000			$ 750,000,000		$ 625,000,000		$ 625,000,000
Number of additional extension periods for debt instrument		2
Debt instrument, term of extension period	1 year
Debt instrument, extension fee (percentage)	1.00%
Description of variable interest rate basis					LIBOR or base rate			LIBOR or base rate			LIBOR or base rate				LIBOR or base rate														LIBOR	LIBOR												base rate			LIBOR
Basis spread on variable interest rate					3.21%	3.30%		4.21%	4.30%				2.37%		3.40%	3.86%															4.00%	3.00%	1.00%		3.00%	3.00%	3.00%	3.50%	3.50%	4.50%	5.50%		3.00%	2.00%	1.00%	2.00%	2.00%	2.00%	2.50%	2.50%	3.50%	4.50%
Debt instrument, fee for unfunded portion of revolving debt (percentage)															0.50%
Percentage of debt hedged by interest rate derivatives			50.00%
Period required to maintain hedge on debt instrument																	3 years
Derivative, notional amount																						850,000,000
Derivative, fixed interest rate																					1.29%
Derivative instrument, term for variable interest rate																																		1 month
Derivative, description of variable rate basis																					LIBOR
Ratio of indebtedness to net capital																							6	4	6.75	11.25	6	4
Interest coverage ratio																									1.50	2.00
Periodic principal payment on debt instrument, (percentage)	0.25%
Debt instrument, prepayment of principal based on excess cash flows (percentage)																		75.00%	50.00%	25.00%
Debt instrument, covenant description																		total leverage ratio is equal to or greater than 6.00:1.00	total leverage ratio is less than 6.00:1.00 but greater than or equal to 4.00:1.00	total leverage ratio is less than 4.00:1.00
Prepayment of principal on debt instrument															$ 15,000,000