Income per Common Share of the Trust (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income (Numerator) [Abstract]
Income from continuing operations net of noncontrolling interest	$ 39,887	$ 39,574
Income from discontinued operations net of noncontrolling interest	14,443	100,607
Net income available to common shareholders	$ 54,330	$ 140,181
Weighted Average Shares (Denominator) [Abstract]
Income from continuing operations net of noncontrolling interest - basic, weighted average shares (in shares)	147,559	147,060
Dilutive shares for long-term compensation plans, weighted average shares (in shares)	981	813
Income from continuing operations net of noncontrolling interest - diluted, weighted average shares (in shares)	148,540	147,873
Common shares
Earnings Per Share, Basic [Abstract]
Income from continuing operations (in usd per share)	$ 0.27	$ 0.27
Income from discontinued operations (in usd per share)	0.10	0.68
Income per common share or unit - basic (in usd per share)	0.37	0.95
Earnings Per Share, Diluted [Abstract]
Income from continuing operations (in usd per share)	0.27	0.27
Income from discontinued operations (in usd per share)	0.10	0.68
Income per common share or unit - diluted (in usd per share)	$ 0.37	$ 0.95