Investments in Unconsolidated Entities (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Investments In Unconsolidated Joint Ventures [Line Items]
Total revenues	$ 3,343,546,000		$ 2,880,608,000		$ 1,805,044,000
Net income	512,300,000		138,280,000		294,840,000
Net real estate investments	22,851,196,000		21,680,221,000
Total other assets	2,163,100,000		1,403,736,000
Total assets	25,014,296,000		23,083,957,000
Total liabilities	11,454,838,000		11,292,587,000
Redeemable noncontrolling interests	86,409,000		35,039,000
Total equity	13,473,049,000		11,756,331,000		10,520,519,000	7,278,647,000
Non Controlling [Member]
Investments In Unconsolidated Joint Ventures [Line Items]
Total revenues	1,875,744,000	[1]	1,678,485,000	[2]	324,941,000
Net income	316,139,000	[1]	(17,064,000)	[2]	10,702,000
Net real estate investments	2,470,623,000		1,589,590,000
Total other assets	998,648,000		564,109,000
Total assets	3,469,271,000		2,153,699,000
Total liabilities	1,778,540,000		1,227,053,000
Redeemable noncontrolling interests	40,525,000		29,482,000
Total equity	$ 1,650,206,000		$ 897,164,000

[1] (1) Beginning February 28, 2014, includes the financial information for the Senior Resource Group unconsolidated entities.

[2] (2) Beginning January 9, 2013, includes the financial information for the Sunrise management company and the unconsolidated Sunrise Senior Living properties.