Credit Concentration (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2018 USD ($) properties		Mar. 31, 2017 USD ($)	Dec. 31, 2017
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	1,257
Percent of NOI	[1],[2]	100.00%
Net Operating Income | $		$ 540,500	[3]	$ 552,129
Credit Concentration (Textual) [Abstract]
Percentage total investments with top five customers					41.00%
Sunrise Senior Living Inc. [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1],[4]	160
Sunrise Senior Living Inc. [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2],[4]	15.00%
Net Operating Income | $	[1],[4]	$ 79,838
Revera [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1],[4]	98
Revera [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2],[4]	7.00%
Net Operating Income | $	[1],[4]	$ 39,525
Brookdale [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	137
Brookdale [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]	7.00%
Net Operating Income | $	[1]	$ 36,865
Genesis HealthCare [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	86
Genesis HealthCare [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]	6.00%
Net Operating Income | $	[1]	$ 34,773
Benchmark Senior Living [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	48
Benchmark Senior Living [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]	4.00%
Net Operating Income | $	[1]	$ 23,948
Remaining Portfolio [Member]
Concentration by investment:
Number of properties in diversified portfolio | properties	[1]	728
Remaining Portfolio [Member] | Net Operating Income [Member]
Concentration by investment:
Percent of NOI	[1],[2]	61.00%
Net Operating Income | $	[1]	$ 325,551

[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] NOI with our top five relationships comprised 41% of total NOI for the year ended December 31, 2017.

[3] 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.

[4] Revera owns a controlling interest in Sunrise Senior Living.