Investment securities - Equity securities and Other long-term investments (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Equity securities
Equity securities and Other long-term investments
Cost or amortized cost	$ 398.4	$ 409.4
Gross unrealized gains	26.2	17.8
Gross unrealized losses	(38.7)	(50.8)
Net foreign currency gains (losses)	8.5	3.6
Fair value	394.4	380.0
Other long-term investments
Equity securities and Other long-term investments
Cost or amortized cost	351.7	337.6
Gross unrealized gains	48.3	32.6
Gross unrealized losses	(20.5)	(13.5)
Net foreign currency gains (losses)	10.2	8.3
Fair value	389.7	365.0
Other long-term investments \| Hedge funds and private equity funds
Equity securities and Other long-term investments
Fair value	301.7	301.4
Other long-term investments \| Limited liability companies and private equity securities
Equity securities and Other long-term investments
Fair value	$ 88.0	$ 63.6

Amount of unrealized gain on investment in debt and equity securities.

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Amount of unrealized loss on investment in debt and equity securities.

+ References

No definition available.

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- Definition

The amount of net foreign currency gains (losses) on investment securities measured at fair value.

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No definition available.

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- Definition

Cost of investment in debt investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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No definition available.

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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