Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012	Dec. 31, 2011
Segment Information [Abstract]
Number of reportable segments					6
Segment Reporting Information [Line Items]
Revenue	$ 728,999		$ 696,145		$ 2,157,733		$ 2,069,326		$ 2,768,738	$ 2,456,483
Segment operating income	218,187		201,470		649,818		612,728
General and administrative (including non-cash stock-based compensation expense)	45,824		43,158		138,470		134,202
Facility lease expense	69,232		71,167		207,028		213,240
Depreciation and amortization	68,644		62,876		200,557		189,781
Asset impairment	504		0		2,658		8,329
Loss on acquisition	0		0		0		636
Gain on facility lease termination	0		0		0		(2,780)
Income from operations	33,983		24,269		101,105		69,320
Total assets	4,644,231				4,644,231				4,665,978
Retirement Centers [Member]
Segment Reporting Information [Line Items]
Revenue	133,272	[1]	126,401	[1]	392,364	[1]	376,726	[1]
Segment operating income	56,820	[2]	50,722	[2]	164,331	[2]	154,388	[2]
Total assets	1,245,316				1,245,316				1,256,497
Assisted Living [Member]
Segment Reporting Information [Line Items]
Revenue	262,524	[1]	254,179	[1]	783,636	[1]	757,930	[1]
Segment operating income	96,750	[2]	91,162	[2]	289,216	[2]	271,891	[2]
Total assets	1,426,868				1,426,868				1,438,934
CCRCs - Rental [Member]
Segment Reporting Information [Line Items]
Revenue	100,076	[1]	96,681	[1]	297,965	[1]	287,051	[1]
Segment operating income	27,013	[2]	25,100	[2]	81,657	[2]	79,883	[2]
Total assets	524,875				524,875				534,220
CCRCs - Entry Fee [Member]
Segment Reporting Information [Line Items]
Revenue	74,110	[1]	71,413	[1]	222,434	[1]	213,990	[1]
Segment operating income	18,218	[2]	15,164	[2]	55,561	[2]	47,486	[2]
Total assets	951,475				951,475				951,584
ISC [Member]
Segment Reporting Information [Line Items]
Revenue	61,162	[1]	56,856	[1]	180,053	[1]	168,432	[1]
Segment operating income	11,764	[2]	11,915	[2]	36,078	[2]	36,730	[2]
Total assets	95,906				95,906				90,357
Management Services [Member]
Segment Reporting Information [Line Items]
Revenue	97,855	[1],[3]	90,615	[1],[3]	281,281	[1],[3]	265,197	[1],[3]
Segment operating income	7,622	[2]	7,407	[2]	22,975	[2]	22,350	[2]
Total assets	$ 399,791				$ 399,791				$ 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.