Customer Concentration (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 properties		Dec. 31, 2011
Concentration by investment: (1)
Number of Properties	973	[1]
Total Investment	$ 17,423,009,000	[2]
Percent of Investment	100.00%	[3]
Customer Concentration (Textuals) [Abstract]
Percentage total investments with top five customers			0.00%
Genesis Health Care LLC [Member]
Concentration by investment: (1)
Number of Properties	177	[1]
Total Investment	2,682,822,000	[2]
Percent of Investment	15.00%	[3]
Merrill Gardens LLC [Member]
Concentration by investment: (1)
Number of Properties	48	[1]
Total Investment	1,084,536,000	[2]
Percent of Investment	6.00%	[3]
Benchmark Senior Living, LLC [Member]
Concentration by investment: (1)
Number of Properties	35	[1]
Total Investment	842,760,000	[2]
Percent of Investment	5.00%	[3]
Remaining Portfolio [Member]
Concentration by investment: (1)
Number of Properties	684	[1]
Total Investment	10,828,842,000	[2]
Percent of Investment	63.00%	[3]
Sunrise Senior Living [Member]
Concentration by investment: (1)
Number of Properties	10	[1]
Total Investment	1,087,357,000	[2]
Percent of Investment	6.00%	[3]
Belmont Village [Member]
Concentration by investment: (1)
Number of Properties	19	[1]
Total Investment	$ 896,692,000	[2]
Percent of Investment	5.00%	[3]

[1] Genesisis in our seniors housing triple-net segment whereas the other top five customers are in our seniors housing operating segment.

[2] Excludes our share of investments in unconsolidated entities. Please see Note 7 for additional information.

[3] Investments with our top five customers comprised 41% of total investments at December 31, 2011