Capital lease obligation (Details) - USD ($) $ in Thousands	Jan. 01, 2015	Dec. 31, 2015	Sep. 30, 2015
Leases, Capital [Abstract]
Lease Term	20 years
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2016 (remainder of fiscal year)		$ 357
2017		534
2018		538
2019		545
2020		550
Thereafter		8,100
Total minimum capital lease payments		10,624
Less amounts representing interest		(6,255)
Present value of net minimum capital lease payments		4,369	$ 4,380
Less current obligation		(455)
Total long term capital lease obligation		3,914
Long-term obligations (less current portion)
Future capital lease rental payments		4,369	4,380
Environmental post-closure monitoring and maintenance activities		749	749
Less amounts due within one year		(542)	(555)
Long-term obligations (less current portion)		$ 4,576	$ 4,574