Shareholders' Equity, Noncontrolling Interests and Other Comprehensive Income - Common Shares and Units - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Restricted shares
Class Of Stock [Line Items]
Restricted stock, shares canceled for tax withholding for share based compensation (in shares)	2,468		3,288
LTIP Units and Restricted Stock
Class Of Stock [Line Items]
Unit based compensation	$ 1.9	$ 2.2	$ 8.4

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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