Partners' Capital, Equity and Incentive Compensation Plans (Summary of Equity Issued) (Details) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) shares
Subsidiary, Sale of Stock [Line Items]
Remaining Expected Proceeds Available	$ 177,844
February 2019 Class A Offering
Subsidiary, Sale of Stock [Line Items]
Shares Settled | shares	4,000
Proceeds from Issuance or Sale of Equity	$ 159,360
February 2019 Class A Offering March 1, 2020
Subsidiary, Sale of Stock [Line Items]
Forward Shares Sold | shares	3,763
Shares Settled | shares	2,832
Proceeds from Issuance or Sale of Equity	$ 109,998
Remaining Expected Proceeds Available	$ 35,799
At Market
Subsidiary, Sale of Stock [Line Items]
Forward Shares Sold | shares	2,864
Remaining Expected Proceeds Available	$ 142,046
Common Stock Maximum Value Authorized	$ 400,000