Acquisitions of Real Estate Property (Details Textuals) (USD $)	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended			1 Months Ended	3 Months Ended	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	May 31, 2011	Jun. 30, 2011 Atria Acquisition [Member]	Jun. 30, 2011 Atria Acquisition [Member]	May 12, 2011 Atria Acquisition [Member]	Jun. 30, 2010 Lillibridge Acquisition [Member]	Dec. 31, 2010 Sunrise Acquisition [Member]	Jun. 30, 2011 Nationwide Health Properties [Member]	Jun. 30, 2011 Nationwide Health Properties [Member]
Acquisitions of Real Estate Property (Textuals) [Abstract]
Purchase price of acquisition of assets								$ 3,400,000,000
Common stock, shares issued, value					1,380,000,000			1,380,000,000
Business acquisition equity interest issued or issuable number of share issued							24,960,000					0.7866
Business acquisition equity interest issued or issuable per share								$ 55.33
Total number of private pay seniors housing communities through acquisition								117
Revenues and net earnings from acquisition						85,700,000	26,200,000
Number of MOB acquired									96
Assumption of mortgage debt									79,500,000	144,000,000
Acquired ownership interest in Lillibridge's property management									100.00%
Percentage of ownership interest in 38 MOBs									100.00%
Percentage of joint venture interest in 24 MOBs									20.00%
Percentage of joint venture interest in 34 MOBs									5.00%
Number of institutional third parties holding majority interests of joint ventures									2
Repaid mortgage debt involved in acquisition									132,700,000
Acquired ownership interest in seventy nine seniors housing communities										100.00%
Number of acquisitions involved in Sunrise's noncontrolling interests										58
Purchased 96 MOBs for aggregate purchase price									381,000,000	186,000,000
Number of seniors housing communities involved with Sunrise										79
Noncontrolling interests acquired represent Seventy Nine Seniors Housing Communities										between 15% and 25%
Purchase price of 5 MOBs										36,600,000
Acquisition related costs	55,807,000	4,207,000	62,256,000	6,526,000		43,500,000	46,700,000				10,400,000	12,300,000
Total acquisition related cost						51,000,000	51,000,000				12,300,000	12,300,000
Number of properties												654
Revenues and net earnings from acquisition											0	0
Acquisition of debt											2,200,000,000	2,200,000,000
Acquisition of Other Assets and Liabilities												8,400,000,000
Equity issued											5,400,000,000	5,400,000,000
Fair value of contingent consideration	44,200,000		44,200,000
Other liabilities, net											$ 800,000,000	$ 800,000,000