Fair Value of Financial Instruments (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Inputs, Level 1 [Member]
Financial Assets:
Cash and Cash Equivalents	$ 259,673	$ 259,266
Restricted Cash	0	0
Total Financial Assets	282,356	280,150
Financial Liabilities:
Total Debt	0	0
Total Financial Liabilities	0	0
Fair Value, Inputs, Level 2 [Member]
Financial Assets:
Cash and Cash Equivalents	0	0
Restricted Cash	22,034	22,044
Total Financial Assets	22,034	22,044
Financial Liabilities:
Total Debt	832,279	828,990
Total Financial Liabilities	832,279	828,990
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial Assets:
Cash and Cash Equivalents	259,673	259,266
Restricted Cash	22,034	22,044
Total Financial Assets	304,390	302,194
Financial Liabilities:
Total Debt	832,279	828,990
Total Financial Liabilities	832,279	828,990
Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Liabilities:
Interest rate swap agreements	0	0
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Liabilities:
Interest rate swap agreements	(6,330)	(5,078)
Interest Rate Swap [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Financial Liabilities:
Interest rate swap agreements	(6,330)	(5,078)
Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Assets:
Equity Securities	22,683	20,884
Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Assets:
Equity Securities	0	0
Equity Securities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Financial Assets:
Equity Securities	$ 22,683	$ 20,884