Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended				12 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010		Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Segment Information [Abstract]
Number of reportable segments					4
Number of communities that moved between segments					4
Segment Reporting Information [Line Items]
Revenue	$ 583,299	[1]	$ 565,518	[1]	$ 1,170,219	[1]	$ 1,126,522	[1]	$ 2,280,535	$ 2,100,274	$ 2,001,304
Segment operating income	198,735	[2]	195,497	[2]	396,799	[2]	384,179	[2]
General and administrative (including non-cash stock-based compensation expense)	33,230	[3]	31,410	[3]	66,351	[3]	62,944	[3]
Facility lease expense	66,065		67,175		132,380		135,424
Depreciation and amortization	70,577		73,168		142,359		146,229
Asset impairment	0		0		14,846		0
Income from operations	28,863		23,744		40,863		39,582
Assets by segment	4,405,764				4,405,764				4,530,470
Retirement Centers [Member]
Segment Reporting Information [Line Items]
Revenue	128,839	[1]	132,209	[1]	257,400	[1]	263,792	[1]
Segment operating income	52,687	[2]	54,963	[2]	104,896	[2]	108,148	[2]
Assets by segment	1,067,934				1,067,934				1,132,934
Assisted Living [Member]
Segment Reporting Information [Line Items]
Revenue	261,716	[1]	254,748	[1]	526,910	[1]	506,244	[1]
Segment operating income	92,844	[2]	91,813	[2]	185,921	[2]	180,599	[2]
Assets by segment	1,444,961				1,444,961				1,433,123
CCRCs [Member]
Segment Reporting Information [Line Items]
Revenue	173,368	[1]	160,603	[1]	347,648	[1]	320,553	[1]
Segment operating income	52,150	[2]	47,733	[2]	103,945	[2]	93,467	[2]
Assets by segment	1,579,076				1,579,076				1,632,755
Management Services [Member]
Segment Reporting Information [Line Items]
Revenue	19,376	[1],[4]	17,958	[1],[4]	38,261	[1],[4]	35,933	[1],[4]
Segment operating income	1,054	[2]	988	[2]	2,037	[2]	1,965	[2]
Assets by segment	$ 313,793				$ 313,793				$ 331,658

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