Commitments and contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended	0 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2011 Cases	Jun. 30, 2014 Cases Lawsuits	May 06, 2014 AA And Saba Consultants [Member]	Dec. 31, 2013 AA And Saba Consultants [Member]	Dec. 31, 2012 AA And Saba Consultants [Member]	Feb. 28, 2014 AA And Saba Consultants [Member]
Loss Contingencies [Line Items]
Number of lawsuits against Company		16
Number of lawsuit		0
Number of active product liability cases	55	16
Amount of settlement offer					$ 0.8
Verdict against the company						3.3
Loss contingency loss in period				2.6
Amount of attorneys' fees, costs and expenses awarded to plaintiff			$ 1.2