Income taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Cumulative unremitted earnings, non-permanently reinvested	$ 471,200
Cumulative unremitted earnings	$ 1,214,900
Effective income tax rate, total	3.30%	3.20%	13.00%
Realized net benefit as result of reducing our reserves with respect to uncertain tax positions	$ 8,800	$ 4,600	$ 1,800
Tax effect, carry forwards	$ 136,000
Percentage of change in ownership	50.00%
Deferred tax assets, valuation allowance	$ 104,520	103,475
Unrecognized tax benefits that would impact effective tax rate	10,400
Unrecognized tax benefits, interest (benefit) expense	200	1,600	1,000
Unrecognized tax benefits, penalties	(500)	(400)	$ (800)
Unrecognized tax benefits, interest (benefit) expense accrued	700	6,500
Unrecognized tax benefits, penalties accrued	2,700	$ 3,200
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	6,500
No Expiration Date
Income Tax Contingency [Line Items]
Tax effect, carry forwards	11,000
After 2013 but before the end of 2018
Income Tax Contingency [Line Items]
Tax effect, carry forwards	1,600
After 2018
Income Tax Contingency [Line Items]
Tax effect, carry forwards	$ 123,400
Excess Tax Deductions
Income Tax Contingency [Line Items]
Effective income tax rate, total	3.30%	3.20%