Fair Value of Financial Instruments - Summary or Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Fair value of financial assets and liabilities
Unrealized losses reclassified to interest expense	$ 678	$ 0
Unrealized losses expected to be reclassified during the next twelve months	2,800
Carrying value
Fair value of financial assets and liabilities
Mortgages payable assumed in connection with acquisitions	297,100		$ 298,400
Notes and bonds payable	5,400,000		5,400,000
Estimated fair value
Fair value of financial assets and liabilities
Mortgages payable assumed in connection with acquisitions	306,800		305,700
Notes and bonds payable	5,632,700		5,430,000
Mortgages Payable
Fair value of financial assets and liabilities
Unamortized balance of non-cash net premiums	4,000		4,400
Remaining balance of deferred financing costs at period end	169		183
Notes and bonds payable
Fair value of financial assets and liabilities
Unamortized balance of non-cash net premiums	10,300		10,500
Remaining balance of deferred financing costs at period end	32,500		33,700
Interest rate swaps | Level 2 | Accounts payable and accrued expenses
Fair value of financial assets and liabilities
Fair value of derivative liabilities	10,400		7,000
Interest rate swaps | Level 2 | Other assets, net
Fair value of financial assets and liabilities
Fair value of derivative assets	$ 1,900		$ 3,000