Acquisitions of Real Estate Property (Details Textuals) (USD $)	3 Months Ended		9 Months Ended			1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended					1 Months Ended	3 Months Ended	9 Months Ended		1 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Jun. 30, 2010 96 MOBs [Member] Lillibridge Acquisition [Member] Building	Jul. 02, 2010 96 MOBs [Member] Lillibridge Acquisition [Member]	Jun. 30, 2010 38 MOBs [Member] Building	Jul. 02, 2010 38 MOBs [Member] Lillibridge Acquisition [Member]	Jun. 30, 2010 24 MOBs [Member] Building	Jul. 02, 2010 24 MOBs [Member] Lillibridge Acquisition [Member]	Jun. 30, 2010 34 MOBs [Member] Building	Jul. 02, 2010 34 MOBs [Member] Lillibridge Acquisition [Member]	Dec. 31, 2010 5 MOBs [Member] Building	Oct. 31, 2011 2 MOBs [Member] Other Acquisition [Member] Property	Sep. 30, 2011 Nationwide Health Properties [Member] Triple-Net Leased Properties [Member]	Sep. 30, 2011 Nationwide Health Properties [Member] Operating Assets [Member]	Sep. 30, 2011 Atria Senior Living Acquisition [Member]	Sep. 30, 2011 Atria Senior Living Acquisition [Member]	May 12, 2011 Atria Senior Living Acquisition [Member] Property	Jul. 02, 2010 Lillibridge Acquisition [Member] Party	Dec. 31, 2010 Minimum [Member] Sunrise Acquisition [Member]	Dec. 31, 2010 Maximum [Member] Sunrise Acquisition [Member]	Dec. 31, 2010 Sunrise Acquisition [Member] Property	Sep. 30, 2011 Nationwide Health Properties [Member]	Sep. 30, 2011 Nationwide Health Properties [Member] Property HousingCommunity	Jul. 02, 2011 Nationwide Health Properties [Member]	Oct. 31, 2011 Other Acquisition [Member] Property	Aug. 31, 2011 Other Acquisition [Member] Property	Sep. 30, 2011 Other Acquisition [Member] Property	Aug. 02, 2011 Seniors Housing Asset [Member]	Oct. 31, 2011 MOBs and Senior housing communities [Member]
Acquisitions of Real Estate Property (Textuals) [Abstract]
Purchase price of acquisition of assets							$ 381,000,000																	$ 186,000,000
Purchase price of seniors housing asset																		3,594,802,000	3,594,802,000						8,318,678,000	8,318,678,000					3,800,000	150,300,000
Value of common stock shares issued related to acquisition																				1,380,000,000							5,400,000,000
Business acquisition equity interests issued or issuable number of shares issued																			24,960,000
Business acquisition equity interest issued or issuable per share																				$ 55.33							$ 53.74
Total number of private pay seniors housing communities through acquisition																				117
Revenues From Properties Acquired																		157,100,000	242,800,000						134,800,000	134,800,000
NOI from properties acquired																		47,500,000	73,700,000						122,900,000	122,900,000
Assumption of mortgage debt																					79,500,000			144,000,000								37,700,000
Acquired Ownership Interest									100.00%		20.00%		5.00%
Acquired ownership interest in Lillibridge's services and development business																					100.00%
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
Number of seniors housing communities involved with Sunrise																								79				2	1
Noncontrolling interests acquired represent Seventy Nine Seniors Housing Communities																						15.00%	25.00%
Purchase price of 5 MOBs														36,600,000
Acquisition related costs	69,350,000	5,142,000	131,606,000	11,668,000														1,500,000	48,200,000						42,500,000	54,800,000
Total acquisition related cost																		52,500,000	52,500,000						54,800,000	54,800,000
Number of Medical office buildings purchased															2
Number of properties acquired						96		38		24		34		5												643
Contingent consideration liability, Fair Value	56,218,000		56,218,000		0													44,200,000	44,200,000	44,200,000
Conversion ratio of acquired entity common stock to parent common stock																											0.7866
Goodwill																		79,200,000	79,200,000						189,600,000	189,600,000
Deferred tax liability																		43,889,000	43,889,000
Amount paid for closing of revolving credit facility																										105,000,000
Allocation of goodwill																$ 129,400,000	$ 60,200,000
Number of shares reduced for working capital adjustment																			83,441
Number of acquired seniors housing operating asset managed by other																														1