Earnings Per Common Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Footnote) (Details) - shares shares in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
RSUs and LTIP Units
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Common shares issued (in shares)	673	1,027	1,143