SENIOR NOTES PAYABLE AND OTHER DEBT (Details 3) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Unsecured revolving credit facility
Debt instruments
Current borrowing capacity	$ 2,000,000,000	$ 2,000,000,000
Maximum borrowing capacity	2,500,000,000	2,500,000,000
Percentage of line of credit facility for negotiated rate loans		50.00%
Facility fee (as a percent)		0.175%
Line of credit facility optional extension period		1 year
Amount outstanding	448,000,000	448,000,000
Letters of credit outstanding	14,900,000	14,900,000
Remaining borrowing capacity	1,540,000,000	1,540,000,000
Unsecured revolving credit facility | Minimum
Debt instruments
Facility fee (as a percent)		0.15%
Unsecured revolving credit facility | Maximum
Debt instruments
Facility fee (as a percent)		0.45%
Letters of credit
Debt instruments
Maximum borrowing capacity	200,000,000	200,000,000
Swingline loans
Debt instruments
Maximum borrowing capacity	200,000,000	200,000,000
Alternative currency loans
Debt instruments
Maximum borrowing capacity	$ 250,000,000	$ 250,000,000
Base rate loans
Debt instruments
Percentage of interest rate	0.10%	0.10%
Base rate loans | LIBOR
Debt instruments
Variable interest rate, basis		LIBOR
Variable interest rate, basis spread on variable rate	1.00%
Base rate loans | Federal funds rate
Debt instruments
Variable interest rate, basis		federal funds rate
Variable interest rate, basis spread on variable rate	0.50%
Eurocurrency rate loans
Debt instruments
Percentage of interest rate	1.10%	1.10%