SEGMENT INFORMATION (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Revenues:
Total revenues	$ 641,950	$ 555,378	$ 1,825,993	$ 1,181,363
Net real estate property:
Total net real estate property	16,919,677		16,919,677		15,913,732
United States
Revenues:
Total revenues	617,605	531,951	1,754,418	1,112,322
Net real estate property:
Total net real estate property	16,514,409		16,514,409		15,510,824
Canada
Revenues:
Total revenues	24,345	23,428	71,575	69,041
Net real estate property:
Total net real estate property	$ 405,268		$ 405,268		$ 402,908