Restructuring costs (Schedule of restructuring expenses) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Restructuring Reserve [Roll Forward]
Beginning balance	$ 5,125
Restructuring charges incurred	155
Cash payments	(1,288)
Ending balance	3,992
Workforce reductions [Member]
Restructuring Reserve [Roll Forward]
Beginning balance	353
Restructuring charges incurred	0
Cash payments	(116)
Ending balance	237
Store closures [Member]
Restructuring Reserve [Roll Forward]
Beginning balance	4,772
Restructuring charges incurred	155
Cash payments	(1,172)
Ending balance	$ 3,755