Cash and Investments - Schedule of Fixed Income Maturity (Details) - Debt securities - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Investment [Line Items]
Amortized cost	$ 20,488.5	$ 9,814.3
Fair value	$ 20,561.5	$ 10,290.8
Effective interest rate	3.50%	4.00%
Due in 1 year or less
Investment [Line Items]
Amortized cost	$ 9,610.5	$ 3,383.9
Fair value	9,606.5	3,537.6
Due after 1 year through 5 years
Investment [Line Items]
Amortized cost	9,112.7	3,540.7
Fair value	9,174.4	3,720.2
Due after 5 years through 10 years
Investment [Line Items]
Amortized cost	808.4	1,017.6
Fair value	802.7	1,054.3
Due after 10 years
Investment [Line Items]
Amortized cost	956.9	1,872.1
Fair value	$ 977.9	$ 1,978.7

Debt Securities, Effective Interest Rate

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- Definition

The amount of financial assets at amortised cost. The amortised cost is the amount at which financial assets are measured at initial recognition minus principal repayments, plus or minus the cumulative amortisation using the effective interest method of any difference between that initial amount and the maturity amount, and adjusted for any impairment. [Refer: Financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2018-01-01
-Paragraph 8
-Subparagraph f
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_8_f&doctype=Standard
-URIDate 2018-03-16

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- Definition

The amount of financial assets that are measured at fair value and for which gains (losses) are recognised in profit or loss. A financial asset shall be measured at fair value through profit or loss unless it is measured at amortised cost or at fair value through other comprehensive income. A gain (loss) on a financial asset measured at fair value shall be recognised in profit or loss unless it is part of a hedging relationship, it is an investment in an equity instrument for which the entity has elected to present gains and losses in other comprehensive income or it is a financial asset measured at fair value through other comprehensive income. [Refer: At fair value [member]; Financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2018-01-01
-Paragraph 8
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=7&date=2018-03-01&anchor=para_8_a&doctype=Standard
-URIDate 2018-03-16

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- Definition

Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

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