Income per Common Share of the Trust (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share, Basic and Diluted [Line Items]
Document Period End Date			Sep. 30, 2019
Income (Numerator) [Abstract]
Income from continuing operations net of noncontrolling interest	$ 59,091	$ 43,713	$ 151,150	$ 91,051
Income from discontinued operations net of noncontrolling interest	41,273	106,430	103,315	218,887
Net income available to common shareholders	$ 100,364	$ 150,143	$ 254,465	$ 309,938
Weighted Average Shares (Denominator) [Abstract]
Income from continuing operations net of noncontrolling interest - basic, weighted average shares (in shares)	150,140	147,324	148,532	147,241
Dilutive shares for long-term compensation plans, weighted average shares (in shares)	839	947	851	919
Income from continuing operations net of noncontrolling interest - diluted, weighted average shares (in shares)	150,979	148,271	149,383	148,160
Common shares
Earnings Per Share, Basic [Abstract]
Income from continuing operations (in usd per share)	$ 0.39	$ 0.30	$ 1.02	$ 0.62
Income from discontinued operations (in usd per share)	0.28	0.72	0.69	1.48
Income per common share or unit - basic (in usd per share)	0.67	1.02	1.71	2.10
Earnings Per Share, Diluted [Abstract]
Income from continuing operations (in usd per share)	0.39	0.29	1.01	0.61
Income from discontinued operations (in usd per share)	0.27	0.72	0.69	1.48
Income per common share or unit - diluted (in usd per share)	$ 0.66	$ 1.01	$ 1.70	$ 2.09