Investments in Unconsolidated Entities (Details) (USD $)	1 Months Ended		12 Months Ended									1 Months Ended
	Aug. 31, 2012	Aug. 31, 2012	Dec. 31, 2013 property	Dec. 31, 2012 property	Dec. 31, 2011	Mar. 31, 2013	Dec. 31, 2013 Minimum	Jul. 31, 2012 Minimum	Dec. 31, 2013 Maximum	Jul. 31, 2012 Maximum	Dec. 31, 2013 ATRIA	Mar. 31, 2013 Two Medical Office Buildings Acquired March 2013 [Member] property	Aug. 31, 2012 Thirty six Medical Office Buildings Acquired in August 2012 [Member] property	Dec. 31, 2013 ATRIA
Equity method investments
Ownership interests in properties accounted for under the equity method (as a percent)						5.00%	5.00%	5.00%	25.00%	20.00%	34.00%			34.00%
Number of properties accounted for under equity method			52	55
Management fees earned in connection with unconsolidated entities			$ 5,800,000	$ 7,300,000	$ 5,700,000
Number of businesses acquired												2	36
Purchase of joint ventures		350,000,000										55,600,000
Notes payable and other debt		101,600,000
Gain on re-measurement of equity method investments	16,600,000											1,300,000
Net investments in unconsolidated entities			91,656,000	95,409,000
(Loss) income from unconsolidated entities			$ (1,748,000)	$ 1,509,000	$ (52,000)