Shareholders' Equity, Noncontrolling Interests and Other Comprehensive Income - Common Shares, Share Repurchases and Dividends and Distributions (Details) - USD ($)				1 Months Ended	3 Months Ended								12 Months Ended
	Nov. 08, 2017	Nov. 08, 2016	Nov. 07, 2016	Jul. 31, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2001	May 10, 2017	May 09, 2017	Dec. 31, 2014
Class of Stock [Line Items]
Common shares, authorized (in shares)					200,000,000				100,000,000				200,000,000	100,000,000			200,000,000	100,000,000
Authorized amount					$ 20,000,000.0								$ 20,000,000.0
Treasury stock, acquired (in shares)													0	0		2,100,000
Remaining authorized repurchase amount					$ 7,500,000								$ 7,500,000
Distributions declared (in dollars per share)					$ 0.27	$ 0.26	$ 0.26	$ 0.26	$ 0.41	$ 0.25	$ 0.25	$ 0.25	$ 1.05	$ 1.16	$ 1.22
ATM Equity Program
Class of Stock [Line Items]
Stock, shares authorized not issued																			$ 200,000,000.0
Restricted Stock
Class of Stock [Line Items]
Restricted stock, shares canceled for tax withholding for share based compensation (in shares)													4,314	3,152
LTIP Units and Restricted Stock
Class of Stock [Line Items]
Unit based compensation													$ 8,400,000	$ 10,900,000
Common Shares
Class of Stock [Line Items]
Issuance of common shares, net of issuance costs (in Shares)														4,830,000
Stock issued during period														$ 175,200,000
Proceeds from issuance of common stock														$ 172,100,000
Common Shares | Forward Sale and Underwritten Public Offering
Class of Stock [Line Items]
Issuance of common shares, net of issuance costs (in Shares)														3,600,000
Stock issued during period														$ 126,800,000
Proceeds from issuance of common stock														$ 124,500,000
Common Shares | ATM Equity Program
Class of Stock [Line Items]
Issuance of common shares, net of issuance costs (in Shares)														4,500,000
Stock issued during period														$ 157,600,000
Proceeds from issuance of common stock														155,700,000
Additional maximum gross proceeds amount				$ 250,000,000.0									250,000,000	250,000,000.0
Sale of Stock, remaining value under program													$ 218,000,000	$ 218,000,000
Regular Quarterly Cash Dividend
Class of Stock [Line Items]
Cash dividends declared, period increase (in dollars per share)	$ 0.01	$ 0.01
Distributions declared (in dollars per share)	$ 0.27	0.26	$ 0.25
Special Cash Dividend
Class of Stock [Line Items]
Cash dividends paid (in dollars per share)		$ 0.15