Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended											12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011 Integer		Dec. 31, 2010		Dec. 31, 2009 Integer
Segment Information [Abstract]
Number of reportable segments												4
Number of communities that moved between segments												4				8
Segment Reporting Information [Line Items]
Revenue	$ 671,971		$ 615,728	$ 583,299	$ 586,920		$ 578,224		$ 575,789	$ 565,518	$ 561,004	$ 2,457,918	[1]	$ 2,280,535	[1]	$ 2,100,274	[1]
Segment Operating Income												792,703	[2]	773,657	[2]	718,775	[2]
General and administrative (including non-cash stock compensation expense)												144,249	[3]	130,032	[3]	132,848	[3]
Facility lease expense												274,858		270,905		272,096
Depreciation and amortization												268,506		292,341		271,935
Facility lease termination expense												0		4,608		0
(Gain) loss on sale of communities, net												0		(3,298)		2,043
Asset impairment												16,892		13,075		10,073
Gain on acquisition												(1,982)		0		0
Income (loss) from operations	19,812	[4]	29,505	28,863	12,000	[4]	17,772	[4]	8,640	23,744	15,838	90,180		65,994		29,780
Total assets	4,466,061						4,530,470					4,466,061		4,530,470		4,649,879
Total interest income												3,538		2,238		2,354
Total expenditures for property, plan and equipment, and leasehold improvements												160,131		93,681		117,453
Retirement Centers [Member]
Segment Reporting Information [Line Items]
Revenue												526,207	[1]	530,161	[1]	496,744	[1]
Segment Operating Income												212,828	[2]	218,816	[2]	213,608	[2]
Depreciation and amortization												60,780		62,510		52,258
Total assets	1,061,815						1,132,934					1,061,815		1,132,934		1,109,806
Total interest income												311		19		55
Total interest expense												28,444		35,222		31,837
Total expenditures for property, plan and equipment, and leasehold improvements												46,344		23,079		11,949
Assisted Living [Member]
Segment Reporting Information [Line Items]
Revenue												1,063,155	[1]	1,023,785	[1]	925,917	[1]
Segment Operating Income												367,691	[2]	361,926	[2]	324,969	[2]
Depreciation and amortization												83,275		92,914		83,144
Total assets	1,463,198						1,433,123					1,463,198		1,433,123		1,519,760
Total interest income												18		17		41
Total interest expense												58,453		63,591		58,855
Total expenditures for property, plan and equipment, and leasehold improvements												44,329		24,911		13,142
CCRCs [Member]
Segment Reporting Information [Line Items]
Revenue												702,395	[1]	653,727	[1]	593,688	[1]
Segment Operating Income												202,667	[2]	189,001	[2]	175,495	[2]
Depreciation and amortization												86,051		86,266		80,594
Total assets	1,563,004						1,632,755					1,563,004		1,632,755		1,690,121
Total interest income												2,298		970		870
Total interest expense												35,640		38,871		33,326
Total expenditures for property, plan and equipment, and leasehold improvements												37,325		28,729		81,720
Management Services [Member]
Segment Reporting Information [Line Items]
Revenue												166,161	[5]	72,862	[5]	83,925	[5]
Segment Operating Income												9,517	[2]	3,914	[2]	4,703	[2]
Depreciation and amortization												38,400		50,651		55,939
Total assets	378,044						331,658					378,044		331,658		330,192
Total interest income												911		1,232		1,388
Total interest expense												19,641		8,038		10,591
Total expenditures for property, plan and equipment, and leasehold improvements												$ 32,133		$ 16,962		$ 10,642

[1] All revenue is earned from external third parties in the United States.

[2] Segment operating income is defined as segment revenues less segment operating expenses (excluding depreciation and amortization).

[3] Net of general and administrative costs allocated to management services reporting segment.

[4] Fourth quarter 2011 and 2010 results include non-cash impairment charges of $2.0 million and $13.1 million, respectively. First quarter 2011 results include non-cash impairment charges of $14.8 million.

[5] Management services segment revenue includes reimbursements for which the Company is the primary obligor of costs incurred on behalf of managed communities.