Capital and Accumulated Other Comprehensive Loss (5.850% Series K Cumulative Redeemable Preferred Units) (Details) - $ / shares	Dec. 31, 2019	Oct. 10, 2019	Jun. 29, 2019	Mar. 15, 2019	Sep. 30, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Preferred stock, issued (shares)					44,450,000	50,650,000
Series K Preferred Units
Class of Stock [Line Items]
Dividend rate percentage				5.85%
Preferred stock, issued (shares)				8,400,000
Preferred stock dividend per share amount (in dollars per share)			$ 0.43875	$ 1.46250
Redemption price (in dollars per share)				$ 25.00
Series L Preferred Units | Subsequent Event
Class of Stock [Line Items]
Dividend rate percentage		5.20%
Preferred stock, issued (shares)		13,800,000
Preferred stock dividend per share amount (in dollars per share)		$ 1.30000
Redemption price (in dollars per share)		$ 25.00
Series L Preferred Units | Subsequent Event | Scenario, Forecast
Class of Stock [Line Items]
Preferred stock dividend per share amount (in dollars per share)	$ 0.29250