Partners' Capital, Equity and Incentive Compensation Plans - Schedule of Quarterly Cash Dividends (Details) - USD ($) $ / shares in Units, $ in Millions							3 Months Ended
	Apr. 15, 2021	Apr. 06, 2021	Jan. 15, 2021	Jan. 07, 2021	Jan. 15, 2020	Jan. 07, 2020	Mar. 31, 2021	Mar. 31, 2020
Series A Preferred Stock
Per Share and Per Unit Rate (in dollars per share)			$ 0.45		$ 0.45
Aggregate Dividend/Distribution Amount			$ 1.9		$ 1.9		$ 1.9	$ 1.9
Series A Preferred Stock | Subsequent Event
Per Share and Per Unit Rate (in dollars per share)	$ 0.45
Series B Preferred Stock
Per Share and Per Unit Rate (in dollars per share)			$ 1.63		$ 1.63
Aggregate Dividend/Distribution Amount			$ 5.1		$ 5.1		5.1	5.1
Series B Preferred Stock | Subsequent Event
Per Share and Per Unit Rate (in dollars per share)	$ 1.63
Common stock
Per Share and Per Unit Rate (in dollars per share)				$ 0.47		$ 0.44
Aggregate Dividend/Distribution Amount				$ 33.4		$ 28.6	$ 33.4	$ 28.6
Common stock | Subsequent Event
Per Share and Per Unit Rate (in dollars per share)		$ 0.50