Commitments and contingencies (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) item
Underpaid revenue share payments and related interest
Other matters
Claim value	$ 4,600
Letter of Credit
Commitments and contingencies
Amount of Letters of Credit that allows entity to draw	$ 4,121
Number of drafts drawn under Letters of Credit | item	0