Fair Value of Financial Instruments (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Assets [Abstract]
Debt Securities		$ 1,791
Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Assets [Abstract]
Debt Securities		0
Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Assets [Abstract]
Debt Securities		0
Debt Securities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Financial Assets [Abstract]
Debt Securities		1,791
Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Assets [Abstract]
Debt Securities	34,970	73,430
Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Assets [Abstract]
Debt Securities	0	0
Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Assets [Abstract]
Debt Securities	0	0
Equity Securities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Financial Assets [Abstract]
Debt Securities	34,970	73,430
Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Liabilities [Abstract]
Interest rate swap agreements	0	0
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Liabilities [Abstract]
Interest rate swap agreements	(5,209)	5,156
Interest Rate Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Liabilities [Abstract]
Interest rate swap agreements		0
Interest Rate Swap [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Financial Liabilities [Abstract]
Interest rate swap agreements	(5,209)	5,156
Fair Value, Inputs, Level 1 [Member]
Financial Assets [Abstract]
Cash and Cash Equivalents	138,668	426,212
Restricted Cash	0	0
Total Financial Assets	173,638	501,433
Financial Liabilities [Abstract]
Long-term Debt	0	0
Total Financial Liabilities	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure		0
Fair Value, Inputs, Level 2 [Member]
Financial Assets [Abstract]
Cash and Cash Equivalents	0	0
Restricted Cash	20,924	21,095
Total Financial Assets	20,924	21,095
Financial Liabilities [Abstract]
Long-term Debt	838,032	727,440
Total Financial Liabilities	838,032	727,440
Foreign Currency Contracts, Liability, Fair Value Disclosure		(971)
Fair Value, Inputs, Level 3 [Member]
Financial Assets [Abstract]
Cash and Cash Equivalents	0	0
Restricted Cash	0	0
Total Financial Assets	0	0
Financial Liabilities [Abstract]
Long-term Debt	0	0
Total Financial Liabilities	0	0
Interest rate swap agreements	0
Foreign Currency Contracts, Liability, Fair Value Disclosure		0
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial Assets [Abstract]
Cash and Cash Equivalents	138,668	426,212
Restricted Cash	20,924	21,095
Total Financial Assets	194,562	522,528
Financial Liabilities [Abstract]
Long-term Debt	838,032	727,440
Total Financial Liabilities	838,032	727,440
Foreign Currency Contracts, Liability, Fair Value Disclosure		$ (971)