Accounting Policies and Related Matters (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) lease	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Accounting Policies [Abstract]
Lease agreements with residents, term	1 year
Lease agreements with residents, cancelable period	30 days
Loss (gain) on derivatives and financial instruments, net	$ 4,016,000	$ (2,284,000)	$ 2,448,000
Other than temporary asset impairment charges		$ 18,294,000
Redeemable noncontrolling interests, carrying value	424,046,000
Current redemption value of redeemable noncontrolling interest that exceeded the carrying value	$ 18,891,000
Property, Plant and Equipment [Line Items]
Number of ground leases and office and equipment leases | lease	139
Operating lease obligations relating to certain ground leases	$ 1,138,046,000
Buildings | Minimum
Property, Plant and Equipment [Line Items]
Properties, estimated useful life	15 years
Buildings | Maximum
Property, Plant and Equipment [Line Items]
Properties, estimated useful life	40 years
Improvements | Minimum
Property, Plant and Equipment [Line Items]
Properties, estimated useful life	5 years
Improvements | Maximum
Property, Plant and Equipment [Line Items]
Properties, estimated useful life	15 years