Senior Notes Payable and Other Debt (Details) (USD $) In Thousands	Jun. 30, 2011		Dec. 31, 2010
Long-term debt and certain interest rate and maturity information
Line of credit	$ 139,500		$ 40,000
Unsecured term loan due 2013	200,000		200,000
Mortgage loans	2,244,441		1,349,521
Total	4,621,374		2,926,954
Capital lease obligations	355,807
Unamortized fair value adjustment	74,150		11,790
Unamortized commission fees and discounts	(44,251)		(38,700)
Senior notes payable and other debt	5,007,080		2,900,044
Principal Amount Due at Maturity [Member]
Long-term debt and certain interest rate and maturity information
Total	4,173,060
Unsecured Revolving Credit Facilities [Member]
Long-term debt and certain interest rate and maturity information
Total	139,500	[1]
Scheduled Periodic Amortization [Member]
Long-term debt and certain interest rate and maturity information
Total	308,814
3 7/8 % percent Convertible Senior Notes due 2011 [Member]
Long-term debt and certain interest rate and maturity information
Senior Notes	230,000		230,000
9% Senior Notes due 2012 [Member]
Long-term debt and certain interest rate and maturity information
Senior Notes	82,433		82,433
3.125% Senior Notes due 2015 [Member]
Long-term debt and certain interest rate and maturity information
Senior Notes	400,000		400,000
6 1/2% Senior Notes due 2016 [Member]
Long-term debt and certain interest rate and maturity information
Senior Notes	400,000		400,000
6 3/4% Senior Notes due 2017 [Member]
Long-term debt and certain interest rate and maturity information
Senior Notes	225,000		225,000
4.750% Senior Notes due 2021 [Member]
Long-term debt and certain interest rate and maturity information
Senior Notes	$ 700,000

[1] June 30, 2011, we had $26.7 million of unrestricted cash and cash equivalents, for $112.8 million of net borrowings outstanding under our unsecured revolving credit facilities.