Income taxes (Reconciliation of Federal Statutory Tax Rate) (Details)	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal statutory tax rate	35.00%	35.00%	35.00%
Foreign earnings, including earnings invested indefinitely	(18.10%)	(22.40%)	(21.30%)
Credits, Puerto Rico Excise Tax	(2.50%)	(4.40%)	(4.70%)
Credits, primarily federal R&D	(1.40%)	(1.50%)	(3.00%)
State taxes	0.10%	0.70%	0.80%
Audit settlements (federal, state, foreign)	(0.50%)	0.00%	(3.70%)
Other, net	0.40%	0.20%	0.40%
Effective tax rate	13.00%	7.60%	3.50%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32698-109319

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-Name Accounting Standards Codification
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to statutory income tax expense (benefit) outside of the country of domicile.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income tax settlements. Including, but not limited to, domestic tax settlement, foreign tax settlement, state and local tax settlement, and other tax settlements.

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