Debt Obligations (Details) - Debt Obligations - USD ($) $ in Thousands	1 Months Ended			9 Months Ended
	Oct. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Debt Instrument [Line Items]
Outstanding principal balance				$ 2,334,888		$ 2,372,521
Finance lease, liability				240		443
Assumed market debt adjustments, net				1,419	$ 1,200	1,218
Deferred financing costs, net				(14,466)	(17,200)	(17,204)
Total				2,319,003		2,354,099
Gross borrowings		$ 200,000		255,000	116,600
Gross payments				255,000	190,000
Proceeds from Lines of Credit		$ 200,000		255,000	116,600
Repayments of Lines of Credit				255,000	190,000
Repayments of Long-term Debt			$ 30,000	37,778	$ 7,973
Fixed-rate debt				1,754,388		2,122,021
Variable-rate debt				580,500		250,500
Unsecured debt				1,622,500		1,652,500
Secured debt				712,388		720,021
Total				$ 2,334,888		$ 2,372,521
Weighted-average interest rate on debt				3.10%		3.40%
Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of Debt	$ 20,400