Credit Concentration (Details)		3 Months Ended			9 Months Ended
		Sep. 30, 2015 USD ($) properties		Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) properties	Sep. 30, 2014 USD ($)	Dec. 31, 2014
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	1,353			1,353
Percent of NOI	[1],[2]				100.00%
Net Operating Income		$ 570,294,000	[1]	$ 492,366,000	$ 1,646,823,000	$ 1,435,435,000
Credit Concentration (Textual) [Abstract]
Percentage total investments with top five customers							49.00%
Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				100.00%
Net Operating Income	[1]				$ 1,646,823,000
Genesis HealthCare [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	180			180
Genesis HealthCare [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				17.00%
Net Operating Income	[1]				$ 273,922,000
Sunrise Senior Living [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1],[3]	147			147
Sunrise Senior Living [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2],[3]				14.00%
Net Operating Income	[1],[3]				$ 225,580,000
Brookdale [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	146			146
Brookdale [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				8.00%
Net Operating Income	[1]				$ 124,843,000
Benchmark Senior Living [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	50			50
Benchmark Senior Living [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				4.00%
Net Operating Income	[1]				$ 73,788,000
Revera [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1],[3]	71			71
Revera [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2],[3]				5.00%
Net Operating Income	[1],[3]				$ 75,973,000
Remaining Portfolio [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	759			759
Remaining Portfolio [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				52.00%
Net Operating Income	[1]				$ 872,717,000

[1] (1)     Genesis Healthcare is in our triple-net segment. Sunrise Senior Living and Revera are in our seniors housing operating segment. Brookdale Senior Living and Benchmark Senior Living are in both our triple-net and seniors housing operating segments.

[2] (2)     NOI with our top five relationships comprised 49% of total NOI for the year ending December 31, 2014

[3] (3) Revera owns a controlling interest in Sunrise Senior Living.