Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 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	$ 690,810		$ 583,299		$ 1,373,855		$ 1,170,219
Segment operating income	206,371		199,186		411,932		397,672
General and administrative (including non-cash stock-based compensation expense)	46,071		33,681		91,044		67,224
Facility lease expense	70,628		66,065		142,073		132,380
Depreciation and amortization	63,561		70,577		126,905		142,359
Asset impairment	7,246		0		8,329		14,846
Loss on acquisition	0		0		636		0
Gain on facility lease termination	0		0		(2,780)		0
Income from operations	18,865		28,863		45,725		40,863
Assets by segment	4,578,321				4,578,321				4,466,061
Retirement Centers [Member]
Segment Reporting Information [Line Items]
Revenue	125,813	[1]	115,916	[1]	250,325	[1]	231,445	[1]
Segment operating income	52,675	[2]	48,924	[2]	103,666	[2]	97,501	[2]
Assets by segment	1,175,952				1,175,952				1,047,388
Assisted Living [Member]
Segment Reporting Information [Line Items]
Revenue	252,399	[1]	237,665	[1]	503,751	[1]	478,893	[1]
Segment operating income	90,166	[2]	86,047	[2]	180,729	[2]	171,722	[2]
Assets by segment	1,429,114				1,429,114				1,451,612
CCRCs - Rental [Member]
Segment Reporting Information [Line Items]
Revenue	95,258	[1]	88,618	[1]	190,370	[1]	178,816	[1]
Segment operating income	26,764	[2]	29,755	[2]	54,783	[2]	59,704	[2]
Assets by segment	545,166				545,166				546,867
CCRCs - Entry Fee [Member]
Segment Reporting Information [Line Items]
Revenue	71,195	[1]	71,390	[1]	143,251	[1]	142,233	[1]
Segment operating income	15,854	[2]	17,987	[2]	32,996	[2]	35,778	[2]
Assets by segment	973,143				973,143				994,064
ISC [Member]
Segment Reporting Information [Line Items]
Revenue	57,722	[1]	50,334	[1]	111,576	[1]	100,571	[1]
Segment operating income	13,413	[2]	14,968	[2]	24,815	[2]	30,057	[2]
Assets by segment	96,021				96,021				78,137
Management Services [Member]
Segment Reporting Information [Line Items]
Revenue	88,423	[1],[3]	19,376	[1],[3]	174,582	[1],[3]	38,261	[1],[3]
Segment operating income	7,499	[2]	1,505	[2]	14,943	[2]	2,910	[2]
Assets by segment	$ 358,925				$ 358,925				$ 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.