Credit Concentration (Details) (USD $)	9 Months Ended
	Sep. 30, 2013 properties		Dec. 31, 2012
Concentration by investment:
Number of properties in diversified portfolio	1,140	[1],[2]
Net real estate investments	$ 21,606,543,000	[1],[2]	$ 17,423,009,000
Percent of Investment	100.00%	[2],[3]
Credit Concentration (Textual) [Abstract]
Percentage total investments with top five customers			37.00%
Genesis HealthCare [Member]
Concentration by investment:
Number of properties in diversified portfolio	177	[1],[2]
Net real estate investments	2,662,196,000	[1],[2]
Percent of Investment	12.00%	[2],[3]
Benchmark Senior Living [Member]
Concentration by investment:
Number of properties in diversified portfolio	37	[1],[2]
Net real estate investments	852,960,000	[1],[2]
Percent of Investment	4.00%	[2],[3]
Remaining Portfolio [Member]
Concentration by investment:
Number of properties in diversified portfolio	740	[1],[2]
Net real estate investments	11,949,624,000	[1],[2]
Percent of Investment	55.00%	[2],[3]
Belmont Village [Member]
Concentration by investment:
Number of properties in diversified portfolio	19	[1],[2]
Net real estate investments	859,797,000	[1],[2]
Percent of Investment	4.00%	[2],[3]
Sunrise Senior Living [Member]
Concentration by investment:
Number of properties in diversified portfolio	120	[1],[2]
Net real estate investments	4,060,818,000	[1],[2]
Percent of Investment	19.00%	[2],[3]
Revera [Member]
Concentration by investment:
Number of properties in diversified portfolio	47	[1],[2]
Net real estate investments	$ 1,221,148,000	[1],[2]
Percent of Investment	6.00%	[2],[3]

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

[2] Genesis is in our seniors housing triple-net segment. Sunrise, Revera, and Belmont Village are in our seniors housing operating segment. Benchmark is in both our seniors housing triple-net and seniors housing operating segments.

[3] Investments with our top five relationships comprised 37% of total investments at December 31, 2012.