Equity, Capital and Other Interests - Changes in Issued and Outstanding Common Shares and Units (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity Capital And Other Interests [Abstract]
Common Stock, Shares, Outstanding	365,870,924	364,755,444	362,855,454
Common Shares Issued:
Conversion of OP Units	1,149,284	88,838	208,307
Exercise of share options	846,137	815,044	1,456,363
Employee Share Purchase Plan (ESPP)	68,286	63,909	68,462
Restricted share grants, net	83,451	147,689	168,142
Common Shares Other:
Conversion of restricted shares to restricted units	0	0	1,284
Common Stock, Shares, Outstanding	368,018,082	365,870,924	364,755,444
Units
Total Units Outstanding	14,626,075	14,427,164	14,298,691
Restricted unit grants, net	291,647	287,749	335,496
Conversion of restricted shares to restricted units	0	0	1,284
Conversion of OP Units to Common Shares	(1,149,284)	(88,838)	(208,307)
Total Units Outstanding	13,768,438	14,626,075	14,427,164
Common Shares And Units Outstanding	381,786,520	380,496,999	379,182,608
Units Ownership Interest in Operating Partnership	3.60%	3.80%	3.80%