Commitments and Contingencies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2017 lease
Commitments and Contingencies Disclosure [Abstract]
Number of communities operated under long-term leases	434
Number of operating leases	290
Number of capital and financing leases	144
Initial lease terms, minimum	10 years
Initial lease terms, maximum	20 years
Renewal options, minimum	5 years
Renewal options, maximum	15 years
Remaining base lease terms, minimum	1 year
Remaining base lease terms, maximum	15 years