Income taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Cumulative unremitted earnings, non-permanently reinvested	$ 481,700
Cumulative unremitted earnings	$ 1,100,600
Effective income tax rate, total	3.20%	13.02%	13.40%
Realized net benefit as result of reducing our reserves with respect to uncertain tax positions	$ 4,600	$ 1,800	$ 7,100
Tax effect, carry forwards	$ 123,300
Percentage of change in ownership	50.00%
Deferred tax assets, valuation allowance	$ 103,475	99,141
Unrecognized tax benefits that would impact effective tax rate	17,700
Unrecognized tax benefits, interest (benefit) expense	1,600	1,000	1,300
Unrecognized tax benefits, penalties	(400)	(800)	$ (800)
Unrecognized tax benefits, interest (benefit) expense accrued	6,500	6,200
Unrecognized tax benefits, penalties accrued	3,200	$ 5,000
Minimum
Income Tax Contingency [Line Items]
Unrecognized tax benefits change within next twelve months due to potential for resolution of foreign and U.S. examinations	0
Maximum
Income Tax Contingency [Line Items]
Unrecognized tax benefits change within next twelve months due to potential for resolution of foreign and U.S. examinations	7,400
No Expiration Date
Income Tax Contingency [Line Items]
Tax effect, carry forwards	10,500
After 2013 but before the end of 2018
Income Tax Contingency [Line Items]
Tax effect, carry forwards	800
After 2018
Income Tax Contingency [Line Items]
Tax effect, carry forwards	$ 112,000
Excess Tax Deductions
Income Tax Contingency [Line Items]
Effective income tax rate, total	3.20%	13.00%