SENIOR NOTES PAYABLE AND OTHER DEBT (Details 3) (USD $)	3 Months Ended								1 Months Ended			1 Months Ended	3 Months Ended		1 Months Ended			1 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Mar. 31, 2012 Unsecured term loan	Mar. 31, 2012 Unsecured term loan due 2015	Dec. 31, 2011 Unsecured term loan due 2015	Mar. 31, 2012 Unsecured term loan due 2017	Dec. 31, 2011 Unsecured term loan due 2017	Feb. 29, 2012 4.25% senior notes due 2022	Mar. 31, 2012 4.25% senior notes due 2022	Dec. 31, 2011 4.25% senior notes due 2022	Mar. 31, 2012 6 1/2% Senior Notes due 2016	Mar. 31, 2012 6 1/2% Senior Notes due 2016	Dec. 31, 2011 6 1/2% Senior Notes due 2016	Apr. 30, 2012 4.00% senior notes due 2019	Mar. 31, 2012 4.750% Senior Notes due 2021	Dec. 31, 2011 4.750% Senior Notes due 2021	Apr. 30, 2012 6 3/4% Senior Notes due 2017	Jun. 30, 2012 6 3/4% Senior Notes due 2017	Mar. 31, 2012 6 3/4% Senior Notes due 2017	Dec. 31, 2011 6 3/4% Senior Notes due 2017	Mar. 31, 2012 9% Senior Notes due 2012	Dec. 31, 2011 9% Senior Notes due 2012	Mar. 31, 2012 3.125% Senior Notes due 2015	Dec. 31, 2011 3.125% Senior Notes due 2015	Mar. 31, 2012 Mortgage loans	Dec. 31, 2011 Mortgage loans
Debt instruments
Principal amount of debt issued									$ 600,000,000						$ 600,000,000
Interest rate (as a percent)									4.25%	4.25%		6.50%	6.50%	6.50%	4.00%	4.75%	4.75%	6.75%		6.75%	6.75%	9.00%	9.00%	3.125%	3.125%
Public Offering Price as a Percent of Par									99.214%						99.489%
Proceeds from issuance of debt									595,300,000						596,900,000
Principal amount of debt redeemed												200,000,000						225,000,000
Senior Note Redemption Price as a Percent of Par												103.25%	103.25%					103.375%
Repayments of senior debt												206,500,000						232,600,000
Net loss on extinguishment of debt	29,544,000	16,520,000											29,700,000						(10,000,000)
Principal amount outstanding	$ 6,179,076,000		$ 6,180,443,000	$ 500,000,000	$ 129,721,000	$ 126,875,000	$ 375,000,000	$ 375,000,000		$ 600,000,000	$ 0	$ 0	$ 0	$ 200,000,000		$ 700,000,000	$ 700,000,000			$ 225,000,000	$ 225,000,000	$ 82,433,000	$ 82,433,000	$ 400,000,000	$ 400,000,000	$ 23,800,000	$ 14,600,000