Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Segment Information [Abstract]
Number of reportable segments					6
Number Of Reportable Segments in Prior Reporting Periods					4
Segment Reporting Information [Line Items]
Revenue	$ 696,482		$ 615,728		$ 2,070,337		$ 1,785,947
Segment operating income	201,807		197,081		613,739		594,753
General and administrative (including non-cash stock-based compensation expense)	43,158		38,711		134,202		105,935
Facility lease expense	71,167		68,314		213,240		200,694
Depreciation and amortization	62,876		64,071		189,781		206,430
Asset impairment	0		0		8,329		14,846
(Gain) loss on acquisition	0		(3,520)		636		(3,520)
Gain on facility lease termination	0		0		(2,780)		0
Income from operations	24,606		29,505		70,331		70,368
Assets by segment	4,587,421				4,587,421				4,466,061
Retirement Centers [Member]
Segment Reporting Information [Line Items]
Revenue	126,401	[1]	119,548	[1]	376,726	[1]	350,993	[1]
Segment operating income	50,722	[2]	49,947	[2]	154,388	[2]	147,448	[2]
Assets by segment	1,179,203				1,179,203				1,047,388
Assisted Living [Member]
Segment Reporting Information [Line Items]
Revenue	254,179	[1]	241,037	[1]	757,930	[1]	719,930	[1]
Segment operating income	91,162	[2]	82,104	[2]	271,891	[2]	253,826	[2]
Assets by segment	1,428,812				1,428,812				1,451,612
CCRCs - Rental [Member]
Segment Reporting Information [Line Items]
Revenue	96,681	[1]	91,628	[1]	287,051	[1]	270,444	[1]
Segment operating income	25,100	[2]	28,957	[2]	79,883	[2]	88,661	[2]
Assets by segment	557,318				557,318				546,867
CCRCs - Entry Fee [Member]
Segment Reporting Information [Line Items]
Revenue	71,750	[1]	71,571	[1]	215,001	[1]	213,804	[1]
Segment operating income	15,501	[2]	18,339	[2]	48,497	[2]	54,117	[2]
Assets by segment	966,470				966,470				994,064
ISC [Member]
Segment Reporting Information [Line Items]
Revenue	56,856	[1]	51,375	[1]	168,432	[1]	151,946	[1]
Segment operating income	11,915	[2]	14,398	[2]	36,730	[2]	44,455	[2]
Assets by segment	95,604				95,604				78,137
Management Services [Member]
Segment Reporting Information [Line Items]
Revenue	90,615	[1],[3]	40,569	[1],[3]	265,197	[1],[3]	78,830	[1],[3]
Segment operating income	7,407	[2]	3,336	[2]	22,350	[2]	6,246	[2]
Assets by segment	$ 360,014				$ 360,014				$ 347,993

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