Other intangible assets (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Finite Lived Intangible Assets
Amortization expense	$ 68	$ 90
Remainder of 2014	204
2015	272
2016	272
2017	272
2018	272
2019	272
Favorable lease assets
Finite Lived Intangible Assets
Amortization expense	33
Favorable lease assets | Minimum
Finite Lived Intangible Assets
Amortization period (in years)	19 years
Favorable lease assets | Maximum
Finite Lived Intangible Assets
Amortization period (in years)	60 years
Internet sites
Finite Lived Intangible Assets
Amortization period (in years)	10 years
Amortization expense	$ 35