Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
BASIC
Income from continuing operations attributable to common shareholders	$ 46,830	$ 47,659	$ 94,937	$ 77,818
Income (loss) from discontinued operations attributable to common shareholders	0	(5)	0	1,682
Net income attributable to common shareholders	$ 46,830	$ 47,654	$ 94,937	$ 79,500
Weighted-average number of common shares outstanding - basic	232,592,998	233,812,062	232,617,901	233,172,422
Income (loss) from continuing operations (in dollars per share)	$ 0.20	$ 0.20	$ 0.41	$ 0.33
Income (loss) from discontinued operations (in dollars per share)	0.00	0.00	0.00	0.01
Net income (loss) attributable to common shareholders (in dollars per share)	$ 0.20	$ 0.20	$ 0.41	$ 0.34
DILUTED
Income from continuing operations attributable to common shareholders	$ 46,830	$ 47,659	$ 94,937	$ 77,818
Impact of assumed conversions	963	764	2,023	1,633
Income from continuing operations attributable to common shareholders	47,793	48,423	96,960	79,451
Income (loss) from discontinued operations attributable to common shareholders	0	(5)	0	1,682
Impact of assumed conversions	0	0	0	0
Income (loss) from discontinued operations attributable to common shareholders	0	(5)	0	1,682
Net income attributable to common shareholders	$ 47,793	$ 48,418	$ 96,960	$ 81,133
Effect of dilutive securities:
Share options (in shares)	273,920	296,501	204,783	369,079
6.00% Convertible Guaranteed Notes (in shares)	1,878,445	1,941,833	1,909,841	2,165,367
OP Units (in shares)	3,818,805	3,852,974	3,819,498	3,852,974
Nonvested common shares (in shares)	481,836	0	418,731	0
Weighted-average common shares outstanding (in shares)	239,046,004	239,903,370	238,970,754	239,559,842
Income from continuing operations (in dollars per share)	$ 0.20	$ 0.20	$ 0.41	$ 0.33
Income (loss) from discontinued operations (in dollars per share)	0.00	0.00	0.00	0.01
Net income (loss) attributable to common shareholders (in dollars per share)	$ 0.20	$ 0.20	$ 0.41	$ 0.34
6% Convertible Guaranteed Note [Member]
Effect of dilutive securities:
Stated interest rate	6.00%	6.00%	6.00%	6.00%	6.00%