Commitments and contingencies - Summary of Other Litigation Matters (Detail) (Pending Litigation [Member], Glowczenski [Member])	6 Months Ended
	Jun. 30, 2014
Pending Litigation [Member] | Glowczenski [Member]
Loss Contingencies [Line Items]
Plaintiff	Glowczenski
Month Served	Oct-04
Jurisdiction	US District Court, ED NY
Claim Type	Wrongful Death
Status	Notice of Appeal filed Sept. 2013; Opening Brief was filed Jan. 2014; Answering Brief filed Apr. 2014.