Borrowing Limits Amounts Outstanding and Amounts Available under Revolving Credit Facility (Detail) (Revolving Credit Facility, USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Oct. 04, 2013	Mar. 31, 2013
Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility	$ 120.0	$ 120.0	$ 120.0	$ 60.0
Outstanding revolving credit facility	59.2	60.2		32.6
Available revolving credit facility	$ 60.8	$ 59.8		$ 27.4

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Amount borrowed under the credit facility as of the balance sheet date.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

+ Details

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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