Rendering
| Component: (Network and Table) |
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| Network | 2352301 - Disclosure - Other Comprehensive Income and Accumulated Other Comprehensive Income (Tables) (http://www.alxn.com/role/OtherComprehensiveIncomeAndAccumulatedOtherComprehensiveIncomeTables) |
| Table | (Implied) |
Slicers (applies to each fact value in each table cell)
| Reporting Entity [Axis] | 0000899866 (http://www.sec.gov/CIK) |
| Other Comprehensive Income and Accumulated Other Comprehensive Income [Abstract] | Period [Axis] |
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2016-01-01 - 2016-12-31 |
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Other Comprehensive Income and Accumulated Other Comprehensive Income [Abstract] | |
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] | The following table summarizes the changes in AOCI, by component, for the years ended December 31, 2016, 2015 and 2014: | | | | | | | | | | | | | | | | | | | | |
| Defined Benefit Pension Plans | | Unrealized Gains (Losses) from Marketable Securities | | Unrealized Gains (Losses) from Hedging Activities | | Foreign Currency Translation Adjustment | | Total Accumulated Other Comprehensive Income (Loss) | Balances, December 31, 2013 | $ | (12 | ) | | $ | — |
| | $ | (4 | ) | | $ | (8 | ) | | $ | (24 | ) | Other comprehensive income before reclassifications | (6 | ) | | — |
| | 110 |
| | (6 | ) | | 98 |
| Amounts reclassified from other comprehensive income | 1 |
| | — |
| | (19 | ) | | — |
| | (18 | ) | Net other comprehensive income (loss) | (5 | ) | | — |
| | 91 |
| | (6 | ) | | 80 |
| Balances, December 31, 2014 | $ | (17 | ) | | $ | — |
| | $ | 87 |
| | $ | (14 | ) | | $ | 56 |
| Other comprehensive income before reclassifications | (2 | ) | | (1 | ) | | 111 |
| | (6 | ) | | 102 |
| Amounts reclassified from other comprehensive income | 9 |
| | — |
| | (105 | ) | | — |
| | (96 | ) | Net other comprehensive income (loss) | 7 |
| | (1 | ) | | 6 |
| | (6 | ) | | 6 |
| Balances, December 31, 2015 | $ | (10 | ) | | $ | (1 | ) | | $ | 93 |
| | $ | (20 | ) | | $ | 62 |
| Other comprehensive income before reclassifications | 2 |
| | — |
| | 46 |
| | (4 | ) | | 44 |
| Amounts reclassified from other comprehensive income | 1 |
| | — |
| | (47 | ) | | — |
| | (46 | ) | Net other comprehensive income (loss) | 3 |
| | — |
| | (1 | ) | | (4 | ) | | (2 | ) | Balances, December 31, 2016 | $ | (7 | ) | | $ | (1 | ) | | $ | 92 |
| | $ | (24 | ) | | $ | 60 |
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Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] | The table below provides details regarding significant reclassifications from AOCI during the years ended December 31, 2016, 2015 and 2014: | | | | | | | | | | | | | | Details about Accumulated Other Comprehensive Income Components | | Amount Reclassified From Accumulated Other Comprehensive Income during the year ended December 31, | | Affected Line Item in the Consolidated Statements of Operations | | 2016 | 2015 | 2014 | | Unrealized Gains (Losses) on Hedging Activity | | | | | | | Effective portion of foreign exchange contracts | | $ | 73 |
| $ | 118 |
| $ | 19 |
| | Net product sales | Ineffective portion of foreign exchange contracts | | — |
| 2 |
| 3 |
| | Foreign currency gain (loss) | | | 73 |
| 120 |
| 22 |
| | | | | (26 | ) | (15 | ) | (3 | ) | | Income tax expense | | | $ | 47 |
| $ | 105 |
| $ | 19 |
| | | Defined Benefit Pension Items | | | | | | | Amortization of prior service costs and actuarial losses | | $ | (1 | ) | $ | (1 | ) | $ | (1 | ) | | (a) | Curtailment | | — |
| (10 | ) | — |
| | (a) | | | (1 | ) | (11 | ) | (1 | ) | | | | | — |
| 2 |
| — |
| | Income tax expense | | | $ | (1 | ) | $ | (9 | ) | $ | (1 | ) | | |
(a) This AOCI component is included in the computation of net periodic pension benefit cost (see Note 16 for additional details). |