Earnings per Common Share - Operating Partnership Units (Details) - Operating Partnership - Noncontrolling Interests - shares	9 Months Ended	12 Months Ended
Sep. 30, 2019	Dec. 31, 2018
Noncontrolling interest
Number of common shares issued for OP unit redeemed by a noncontrolling interest unit holder	1
Units held by noncontrolling interest unit holders	1,117,169	1,117,169

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