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Income Taxes (Narrative) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Jun. 30, 2015 | Jun. 30, 2014
Income Tax [Line Items] |  |
Income tax expense | $ 256 | $ 185
Income tax benefit discrete items | 5 | 12
Unrecognized tax benefits | 497 |
Unrecognized tax benefits that would impact income tax expense and the effective tax rate | 337 |
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit | 131 |
Income tax examination, penalties and interest expense | 6 | 4
Accrued interest and penalties on unrecognized tax benefits | 75 | 161
Canada revenue agency assessments |  |
Income Tax [Line Items] |  |
Income tax expense to settle transfer pricing | $ 12 |
Internal revenue service (IRS) |  |
Income Tax [Line Items] |  |
Income tax benefit discrete items |  | $ 17

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- Definition The sum of the amounts of estimated penalties and interest recognized in the period arising from income tax examinations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319 + Details
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- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Income Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6515339 + Details
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