Derivative Financial Instruments Income Statement Location (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Gain on ineffective portion of derivatives	$ 1,279	$ 47,078
Gain (loss) on foreign currency derivatives	200	(400)
Net effect of swaps	(1,492)	(13,119)	18,194
Amended 2010 Credit Agreement [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Length of initial agreement covenant requirement (years)	3 years
Aggregate term debt and senior notes subject to interest rate protection requirement	50.00%
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amortization of deferred hedge gains	16	33,600
Designated As Hedging [Member] | Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in accumulated OCI on derivatives (effective portion)	140	(35,353)
Designated As Hedging [Member] | Interest Rate Swap [Member] | Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) reclassified from accumulated OCI into income (effective portion)	(12,027)	(3,023)
Designated As Hedging [Member] | Interest Rate Swap [Member] | Net Effect of Swaps [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) recognized in income on derivative (ineffective portion)	0	47,987
Not Designated As Hedging [Member] | Net Effect of Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) recognized in income on derivative	1,279	(909)
Not Designated As Hedging [Member] | Interest Rate Swap [Member] | Net Effect of Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) recognized in income on derivative	0	(3,342)
Not Designated As Hedging [Member] | Foreign Currency Swap [Member] | Net Effect of Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) recognized in income on derivative	6,278	(13,665)
Not Designated As Hedging [Member] | Cross-Currency Swap [Member] | Net Effect of Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount and location of gain (loss) recognized in income on derivative	(4,999)	16,098
September 2010 and March 2011 Swaps [Member] | Forward Starting Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net effect of swaps	$ (3,300)