Restructuring - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended	30 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2017 store	Jun. 30, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Total Restructuring Expenses	$ 537	$ 845	$ 561	$ 14,617
Restructuring Program 2016 and 2017
Restructuring Cost and Reserve [Line Items]
Total Restructuring Expenses						$ 38,800
Gain on Sale of Closed Store Properties
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, number of store closures | store					139
Total Restructuring Expenses	$ (49)	$ 0	$ (376)	0
DAMI | Restructuring Program 2016
Restructuring Cost and Reserve [Line Items]
Total Restructuring Expenses				$ 300