SENIOR NOTES PAYABLE AND OTHER DEBT (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Unsecured line of credit	Jun. 30, 2014 Unsecured revolving credit facilities	Dec. 31, 2013 Unsecured revolving credit facilities	Jun. 30, 2014 6.25% Senior Notes due 2013	Dec. 31, 2013 6.25% Senior Notes due 2013	Jun. 30, 2014 3.125% Senior Notes due 2015	Dec. 31, 2013 3.125% Senior Notes due 2015	Jun. 30, 2014 6% Senior Notes due 2015	Dec. 31, 2013 6% Senior Notes due 2015	Jun. 30, 2014 1.55% Senior Notes due 2016	Dec. 31, 2013 1.55% Senior Notes due 2016	Jun. 30, 2014 1.250% Senior Notes due 2017	Apr. 28, 2014 1.250% Senior Notes due 2017	Jun. 30, 2014 2.00% Senior Notes due 2018	Dec. 31, 2013 2.00% Senior Notes due 2018	Jun. 30, 2014 Unsecured Term Loan Due 2018	Dec. 31, 2013 Unsecured Term Loan Due 2018	Jun. 30, 2014 Unsecured Term Loan Due 2019	Dec. 31, 2013 Unsecured Term Loan Due 2019	Jun. 30, 2014 4.00% senior notes due 2019	Dec. 31, 2013 4.00% senior notes due 2019	Jun. 30, 2014 2.700% Senior Notes due 2020	Dec. 31, 2013 2.700% Senior Notes due 2020	Jun. 30, 2014 4.750% Senior Notes due 2021	Dec. 31, 2013 4.750% Senior Notes due 2021	Jun. 30, 2014 4.25% senior notes due 2022	Dec. 31, 2013 4.25% senior notes due 2022	Jun. 30, 2014 3.25% senior notes due 2022	Dec. 31, 2013 3.25% senior notes due 2022	Jun. 30, 2014 3.750% Senior Notes due 2024	Apr. 28, 2014 3.750% Senior Notes due 2024	Jun. 30, 2014 6.90% Senior Notes due 2037	Dec. 31, 2013 6.90% Senior Notes due 2037	Jun. 30, 2014 6.59% Senior Notes due 2038	Dec. 31, 2013 6.59% Senior Notes due 2038	Jun. 30, 2014 5.45% Senior Notes due 2043	Dec. 31, 2013 5.45% Senior Notes due 2043	Jun. 30, 2014 5.70% Senior Notes due 2043	Dec. 31, 2013 5.70% Senior Notes due 2043	Jun. 30, 2014 Mortgage loans and other	Dec. 31, 2013 Mortgage loans and other	Jun. 30, 2014 Unsecured term loan	Jun. 30, 2014 Unsecured term loan Canada, Dollars	Jun. 30, 2014 Mortgage Loans Held-for-Sale	Dec. 31, 2013 Mortgage Loans Held-for-Sale
Debt instruments
Total Maturities	$ 9,576,777,000	$ 9,320,477,000		$ 179,373,000	$ 376,343,000			$ 400,000,000	$ 400,000,000	$ 234,420,000	$ 234,420,000	$ 550,000,000	$ 550,000,000	$ 300,000,000		$ 700,000,000	$ 700,000,000	$ 200,000,000	$ 200,000,000	$ 800,175,000	$ 800,702,000	$ 600,000,000	$ 600,000,000	$ 500,000,000	$ 500,000,000	$ 700,000,000	$ 700,000,000	$ 600,000,000	$ 600,000,000	$ 500,000,000	$ 500,000,000	$ 400,000,000		$ 52,400,000	$ 52,400,000	$ 22,973,000	$ 22,973,000	$ 258,750,000	$ 258,750,000	$ 300,000,000	$ 300,000,000	$ 2,278,686,000	$ 2,524,889,000	$ 1,000,000,000	$ 116,600,000	$ 44,100,000	$ 13,100,000
Unamortized fair value adjustment	52,140,000	69,611,000
Unamortized discounts	(26,478,000)	(25,096,000)
Senior notes payable and other debt	9,602,439,000	9,364,992,000
Interest rate (as a percent)						6.25%	6.25%	3.125%	3.125%	6.00%	6.00%			1.25%	1.25%	2.00%	2.00%					4.00%	4.00%	2.70%	2.70%	4.75%	4.75%	4.25%	4.25%	3.25%	3.25%	3.75%	3.75%	6.90%	6.90%	6.59%	6.59%	5.45%	5.45%
Amount outstanding			$ 6,400,000	$ 179,400,000