Accumulated other comprehensive loss - Components of Changes in Accumulated Other Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ (382)
Unrealized gain on cross-currency swap and warrants, net of tax	665	103
Foreign currency translation adjustment	(4,860)	376
Ending Balance	(4,577)
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(482)
Foreign currency translation adjustment	(4,860)
Ending Balance	(5,342)
Change in Fair Value [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance			100
Ending Balance	765		100
Change in Fair Value [Member] | Cross-Currency Swap and Warrants [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Unrealized gain on cross-currency swap and warrants, net of tax	665
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(382)
Foreign currency translation adjustment	(4,860)
Ending Balance	(4,577)
Accumulated Other Comprehensive Loss [Member] | Cross-Currency Swap and Warrants [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Unrealized gain on cross-currency swap and warrants, net of tax	$ 665