Acquisitions of Real Estate Property (Details) (USD $)	3 Months Ended																12 Months Ended																12 Months Ended						12 Months Ended											1 Months Ended		1 Months Ended				1 Months Ended				12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Triple Net Leased Properties	Dec. 31, 2012 Triple Net Leased Properties	Dec. 31, 2011 Triple Net Leased Properties	Dec. 31, 2013 Senior Living Operations	Dec. 31, 2012 Senior Living Operations	Dec. 31, 2011 Senior Living Operations	Dec. 31, 2013 MOB Operations	Dec. 31, 2012 MOB Operations	Dec. 31, 2011 MOB Operations	Dec. 31, 2013 2013 Acquisitions	Dec. 31, 2013 2013 Acquisitions Triple Net Leased Properties	Dec. 31, 2013 2013 Acquisitions Senior Living Operations	Dec. 31, 2013 2013 Acquisitions MOB Operations	Dec. 31, 2013 2013 Acquisitions Seniors Housing Communities Triple Net Leased Properties property	Dec. 31, 2013 2013 Acquisitions Seniors Housing Communities Triple Net Leased Properties Corporate Joint Venture property	Dec. 31, 2013 2013 Acquisitions Seniors Housing Communities Senior Living Operations property	Dec. 31, 2013 2013 Acquisitions Medical Office Buildings MOB Operations property	Dec. 31, 2013 Development projects	Dec. 31, 2012 Development projects	Dec. 31, 2013 Development projects Seniors Housing Communities property	Dec. 31, 2012 Development projects Seniors Housing Communities property	Dec. 31, 2013 Development projects Medical Office Buildings property	Dec. 31, 2012 Development projects Medical Office Buildings property	Dec. 31, 2013 Development projects Hospitals property	Dec. 31, 2012 2012 Acquisitions	Dec. 31, 2012 2012 Acquisitions Triple Net Leased Properties	Dec. 31, 2012 2012 Acquisitions Senior Living Operations	Dec. 31, 2012 2012 Acquisitions MOB Operations	Dec. 31, 2012 ATRIA	Dec. 31, 2012 Funds Previously Managed by LFREI	Apr. 30, 2012 Cogdell Spencer Inc	Dec. 31, 2012 Cogdell Spencer Inc	Apr. 30, 2012 Cogdell Spencer Inc Medical Office Buildings property	May 31, 2012 SUNRISE Seniors Housing Communities property	May 31, 2011 ASLG	May 12, 2011 ASLG	May 31, 2011 ASLG Private Pay Seniors Housing Communities property	May 31, 2011 ASLG Development Land Parcel property	Jul. 31, 2011 NHP	Jul. 31, 2011 NHP Seniors Housing and Healthcare Properties	Dec. 31, 2011 Other Acquisitions	Dec. 31, 2012 Other Acquisitions Seniors Housing Communities property	Dec. 31, 2011 Other Acquisitions Seniors Housing Communities property	Dec. 31, 2012 Other Acquisitions Skilled Nursing Facilities property	Dec. 31, 2012 Other Acquisitions Medical Office Buildings property	Dec. 31, 2011 Other Acquisitions Medical Office Buildings property	Dec. 31, 2013 Other Acquisitions Medical Office Buildings Unconsolidated Properties property	Dec. 31, 2012 Other Acquisitions Medical Office Buildings Unconsolidated Properties property
Business Combinations
Number of real estate properties acquired																																	27	1	24	11																71	16			117	1		643		21	5	2	44	14	2	36
Business Combination, consideration transferred																																	$ 860,000,000		$ 770,000,000	$ 150,000,000														$ 760,000,000										$ 329,500,000
Settlement of capital lease obligation																	142,200,000
Number of real estate properties acquired, previously capital leases																																			8
Revenues	732,856,000	[1]	710,924,000	[1]	683,764,000	[1]	682,509,000	[1]	655,730,000	[2]	637,218,000	[2]	610,188,000	[2]	564,597,000	[2]	2,810,053,000	2,467,733,000	1,731,704,000	880,346,000	822,438,000	629,940,000	1,406,005,000	1,227,124,000	865,800,000	462,184,000	377,152,000	200,333,000		21,300,000	38,300,000					10,700,000
NOI																	1,690,059,000	1,490,322,000	1,058,324,000	880,346,000	822,438,000	629,940,000	449,321,000	386,102,000	277,705,000	300,921,000	241,869,000	116,264,000			15,400,000					6,800,000
Net real estate property	18,075,586,000								17,111,532,000								18,075,586,000	17,111,532,000																			65,500,000	116,900,000
Business acquisition, transaction costs	12,800,000																12,800,000																																		28,600,000
Merger-related expenses and deal costs																	21,634,000	63,183,000	153,923,000										12,000,000
Ownership interests in properties accounted for under the equity method (as a percent)							5.00%																																									34.00%
Unit conversion factor for common stock	0.7866																0.7866																																									0.7866
Common stock acquired in business combination, shares	3,712,000								3,699,000								3,712,000	3,699,000																															3,700,000
Preacquisition contingency, amount of settlement																																																	44,000,000
Number of real estate properties acquired, managed by property management business																																																				44
Business combination, joint venture partners' share of net debt assumed																																																		36,300,000
Business combination, right to receive cash, per share of common stock outstanding (in dollars per share)																																																		$ 4.25
Preferred stock, dividend rate, percentage																																																		8.50%
Business combination, consideration transferred per share of preferred stock (in dollars per share)																																																		$ 25.00
Business combination, notes payable and other debt assumed																													41,436,000	36,300,000	5,136,000	0												412,825,000	57,219,000	0	355,606,000			203,800,000										134,900,000
Number of real estate properties completed																																							2	2	1	3	1
Business acquisition equity interests issued or issuable, number of shares issued																																																						24,958,543
Value of common stock shares issued related to acquisition																																																							1,380,000,000
Closing price on acquisition date used to value shares issued in the acquisition (in dollars per share)																																																							$ 55.33
Amount paid for closing of revolving credit facility																																																										$ 105,000,000

[1] The amounts presented for the three months ended March 31, 2013, June 30, 2013 and September 30, 2013 differ from the amounts previously reported in our Quarterly Reports on Form 10-Q as a result of discontinued operations consisting of properties sold in 2013 or classified as held for sale as of December 31, 2013.

[2] The amounts presented for the three months ended March 31, 2012, June 30, 2012, September 30, 2012 and December 31, 2012 differ from the amounts previously reported in our Annual Report on Form 10-K for the year ended December 31, 2012 as a result of discontinued operations consisting of properties sold in 2013 or classified as held for sale as of December 31, 2013.