Credit Concentration (Details) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2016 USD ($) properties		Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) properties		Sep. 30, 2015 USD ($)	Dec. 31, 2015
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	1,399			1,399
Percent of NOI	[1],[2]				100.00%
Net Operating Income | $		$ 605,453	[1]	$ 570,294	$ 1,820,690	[1]	$ 1,646,823
Credit Concentration (Textual) [Abstract]
Percentage total investments with top five customers								46.00%
Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				100.00%
Genesis HealthCare [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	185			185
Genesis HealthCare [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				16.00%
Net Operating Income | $	[1]				$ 293,406
Sunrise Senior Living [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1],[3]	151			151
Sunrise Senior Living [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2],[3]				13.00%
Net Operating Income | $	[1],[3]				$ 234,313
Brookdale [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	148			148
Brookdale [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				7.00%
Net Operating Income | $	[1]				$ 126,824
Benchmark Senior Living [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	49			49
Benchmark Senior Living [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				4.00%
Net Operating Income | $	[1]				$ 73,524
Revera [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1],[3]	97			97
Revera [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2],[3]				6.00%
Net Operating Income | $	[1],[3]				$ 112,211
Remaining Portfolio [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	769			769
Remaining Portfolio [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]				54.00%
Net Operating Income | $	[1]				$ 980,412

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

[2] (2) NOI with our top five relationships comprised 46% of total NOI for the year ending December 31, 2015.

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