Fair Value Measurements (Financial Liabilities Not Measured At Fair Value But For Which Fair Value Is Required To Be Disclosed) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011
Bank lines of credit	$ 162,053	$ 291,983	$ 104,034
Senior unsecured notes	142,501	147,721	160,634
2009 Convertible Notes	225,544	220,642	222,238
Total	530,098	660,346	486,906
Level 1 [Member]
Bank lines of credit
Senior unsecured notes
2009 Convertible Notes
Total
Level 2 [Member]
Bank lines of credit	162,053	291,983	104,034
Senior unsecured notes	142,501	147,721	160,634
2009 Convertible Notes	225,544	220,642	222,238
Total	530,098	660,346	486,906
Level 3 [Member]
Bank lines of credit
Senior unsecured notes
2009 Convertible Notes
Total
Carrying Value [Member]
Bank lines of credit	156,113	280,839	104,034
Senior unsecured notes	143,977	149,394	161,667
2009 Convertible Notes	107,818	107,058	104,871
Total	$ 407,908	$ 537,291	$ 370,572