Partners' Capital, Equity and Incentive Compensation Plans (Summary of Equity Issued) (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Subsidiary, Sale of Stock [Line Items]
Shares and net proceeds available as of December 31, 2019	3,795
Shares and net proceeds available as of December 31, 2019	$ 173,776
Forward Shares Sold/Settled , Number of Shares	9,961	3,795
Proceeds From Issuance Or Sale Of Equity1	$ 587,550	$ 173,776
Proceeds from issuance or sale of equity		177,800
Dividends, common stock		$ 4,000
February 2019 Offering - Settlement
Subsidiary, Sale of Stock [Line Items]
Forward shares (Settled) (in shares)	(931)
Net Proceeds (Received)	$ (35,841)
June '19 ATM
Subsidiary, Sale of Stock [Line Items]
Forward shares (Settled) (in shares)	(4,981)
Forward Shares Sold (in shares)	4,550
Net Proceeds (Received)	$ (250,496)
Net Proceeds Available	$ 243,577
May 2020 Current ATM Program - Sales
Subsidiary, Sale of Stock [Line Items]
Forward Shares Sold (in shares)	3,128
Net Proceeds Available	$ 189,640
June 2020 Offering - Sales
Subsidiary, Sale of Stock [Line Items]
Forward Shares Sold (in shares)	4,400
Net Proceeds Available	$ 266,894