Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended				12 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012	Dec. 31, 2011
Segment Information [Abstract]
Number of reportable segments					6
Segment Reporting Information [Line Items]
Revenue	$ 716,468		$ 690,473		$ 1,428,734		$ 1,373,181		$ 2,768,738	$ 2,456,483
Segment operating income	212,655		206,034		431,631		411,258
General and administrative (including non-cash stock-based compensation expense)	46,035		46,071		92,646		91,044
Facility lease expense	68,777		70,628		137,796		142,073
Depreciation and amortization	67,254		63,561		131,913		126,905
Asset impairment	2,154		7,246		2,154		8,329
Loss on acquisition	0		0		0		636
Gain on facility lease termination	0		0		0		(2,780)
Income from operations	28,435		18,528		67,122		45,051
Total assets	4,630,842				4,630,842				4,665,978
Retirement Centers [Member]
Segment Reporting Information [Line Items]
Revenue	130,170	[1]	125,813	[1]	259,092	[1]	250,325	[1]
Segment operating income	54,177	[2]	52,675	[2]	107,511	[2]	103,666	[2]
Total assets	1,251,500				1,251,500				1,256,497
Assisted Living [Member]
Segment Reporting Information [Line Items]
Revenue	260,497	[1]	252,399	[1]	521,112	[1]	503,751	[1]
Segment operating income	96,181	[2]	90,166	[2]	192,466	[2]	180,729	[2]
Total assets	1,423,997				1,423,997				1,438,934
CCRCs - Rental [Member]
Segment Reporting Information [Line Items]
Revenue	97,562	[1]	95,258	[1]	197,889	[1]	190,370	[1]
Segment operating income	25,567	[2]	26,764	[2]	54,644	[2]	54,783	[2]
Total assets	525,063				525,063				534,220
CCRCs - Entry Fee [Member]
Segment Reporting Information [Line Items]
Revenue	74,016	[1]	70,858	[1]	148,324	[1]	142,577	[1]
Segment operating income	17,772	[2]	15,517	[2]	37,343	[2]	32,322	[2]
Total assets	957,729				957,729				951,584
ISC [Member]
Segment Reporting Information [Line Items]
Revenue	58,693	[1]	57,722	[1]	118,891	[1]	111,576	[1]
Segment operating income	11,214	[2]	13,413	[2]	24,314	[2]	24,815	[2]
Total assets	90,252				90,252				90,357
Management Services [Member]
Segment Reporting Information [Line Items]
Revenue	95,530	[1],[3]	88,423	[1],[3]	183,426	[1],[3]	174,582	[1],[3]
Segment operating income	7,744	[2]	7,499	[2]	15,353	[2]	14,943	[2]
Total assets	$ 382,301				$ 382,301				$ 394,386

[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.