Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 1,008,949	$ 1,120,062	$ 3,070,450	$ 3,462,496
Private pay
Disaggregation of Revenue [Line Items]
Revenue	642,165	682,408	1,931,066	2,160,929
Government reimbursement
Disaggregation of Revenue [Line Items]
Revenue	126,795	129,075	383,252	395,407
Other third-party payor programs
Disaggregation of Revenue [Line Items]
Revenue	32,277	28,696	98,261	86,078
Total resident fee revenue
Disaggregation of Revenue [Line Items]
Revenue	801,237	840,179	2,412,579	2,642,414
Independent Living | Private pay
Disaggregation of Revenue [Line Items]
Revenue	136,274	143,963	406,667	459,875
Independent Living | Government reimbursement
Disaggregation of Revenue [Line Items]
Revenue	600	668	1,852	2,446
Independent Living | Other third-party payor programs
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Independent Living | Total resident fee revenue
Disaggregation of Revenue [Line Items]
Revenue	136,874	144,631	408,519	462,321
Assisted Living and Memory Care | Private pay
Disaggregation of Revenue [Line Items]
Revenue	435,367	464,719	1,310,867	1,482,789
Assisted Living and Memory Care | Government reimbursement
Disaggregation of Revenue [Line Items]
Revenue	17,107	18,406	50,358	54,643
Assisted Living and Memory Care | Other third-party payor programs
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Assisted Living and Memory Care | Total resident fee revenue
Disaggregation of Revenue [Line Items]
Revenue	452,474	483,125	1,361,225	1,537,432
CCRCs | Private pay
Disaggregation of Revenue [Line Items]
Revenue	70,353	73,567	212,978	217,680
CCRCs | Government reimbursement
Disaggregation of Revenue [Line Items]
Revenue	19,931	20,901	61,614	65,986
CCRCs | Other third-party payor programs
Disaggregation of Revenue [Line Items]
Revenue	9,820	9,679	30,492	30,346
CCRCs | Total resident fee revenue
Disaggregation of Revenue [Line Items]
Revenue	100,104	104,147	305,084	314,012
Health Care Services | Private pay
Disaggregation of Revenue [Line Items]
Revenue	171	159	554	585
Health Care Services | Government reimbursement
Disaggregation of Revenue [Line Items]
Revenue	89,157	89,100	269,428	272,332
Health Care Services | Other third-party payor programs
Disaggregation of Revenue [Line Items]
Revenue	22,457	19,017	67,769	55,732
Health Care Services | Total resident fee revenue
Disaggregation of Revenue [Line Items]
Revenue	$ 111,785	$ 108,276	$ 337,751	$ 328,649