Changes in accumulated other comprehensive income (loss) (Detail) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance		$ (24,161)	$ (8,844)
Other Comprehensive loss		(5,987)	(3)
Amounts reclassified from accumulated other comprehensive income	[1]	274	223
Ending Balance		(29,874)	(8,624)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance		(6,586)	6,128
Other Comprehensive loss		(5,987)	(3)
Amounts reclassified from accumulated other comprehensive income		0	0
Ending Balance		(12,573)	6,125
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance		(17,575)	(14,972)
Other Comprehensive loss		0	0
Amounts reclassified from accumulated other comprehensive income	[1]	274	223
Ending Balance		$ (17,301)	$ (14,749)

[1] Amount represents amortization of actuarial losses, a component of net periodic benefit cost. This amount was $0.3 million net of $0.2 million tax benefit and $0.2 million net of a $0.1 million tax benefit for the six months ended June 30, 2015 and 2014, respectively. For the quarters ended June 30, 2015 and 2014, this amount was $0.1 million net of a $0.1 million tax benefit.