Investments in Debt and Equity Securities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013 Investment	Dec. 31, 2012 Investment
Unrealized Losses On Investments [Line Items]
Number of investments in an unrealized loss position	129	30
Foreign Government Debt \| Canada
Unrealized Losses On Investments [Line Items]
Foreign debt securities	$ 133.8	$ 143.0
Foreign Government Debt \| United Kingdom
Unrealized Losses On Investments [Line Items]
Foreign debt securities	$ 25.2	$ 22.4

Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (b)(3)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant