Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair value of financial assets and liabilities
Unrealized gains and losses reclassified to interest expense	$ 520	$ 0	$ 0
Gain and losses expected to be reclassified during next twelve months	2,800
Level 2 | Interest rate swaps | Accounts payable and accrued expenses
Fair value of financial assets and liabilities
Fair value of derivative liabilities	7,000	500
Level 2 | Interest rate swaps | Other assets, net
Fair value of financial assets and liabilities
Fair value of derivative assets	3,000	1,700
Mortgages Payable
Fair value of financial assets and liabilities
Unamortized balance of non-cash net premiums	4,400	5,900
Remaining balance of deferred financing costs at period end	(183)	(236)
Notes and bonds payable
Fair value of financial assets and liabilities
Unamortized balance of non-cash net premiums	10,500	14,300
Remaining balance of deferred financing costs at period end	(33,700)	(34,100)
Carrying value
Fair value of financial assets and liabilities
Notes receivable issued in connection with property sales		5,300
Mortgages payable assumed in connection with acquisitions	298,400	320,300
Notes and bonds payable	5,400,000	5,250,000
Estimated fair value
Fair value of financial assets and liabilities
Notes receivable issued in connection with property sales		5,300
Mortgages payable assumed in connection with acquisitions	305,700	334,200
Notes and bonds payable	$ 5,430,000	$ 5,475,300