Partners' Capital, Equity and Incentive Compensation Plans (Summary of Equity Issued) (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Subsidiary, Sale of Stock [Line Items]
Forward Shares Sold	5,781	3,795
Proceeds from Issuance or Sale of Equity	$ 83,331
Remaining Expected Proceeds Available	$ 304,448	$ 177,845
February 2019 Offering
Subsidiary, Sale of Stock [Line Items]
Forward Shares Sold	(931)
Proceeds from Issuance or Sale of Equity	$ 35,841
Remaining Expected Proceeds Available	$ (35,841)
ATM Program - Settlements
Subsidiary, Sale of Stock [Line Items]
Forward Shares Sold	(1,000)
Proceeds from Issuance or Sale of Equity	$ 47,490
Remaining Expected Proceeds Available	$ (47,490)
ATM Program - Sales
Subsidiary, Sale of Stock [Line Items]
Forward Shares Sold	3,917
Remaining Expected Proceeds Available	$ 209,934