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Investments - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amount of restricted investments sold	$ 9,965us-gaap_ProceedsFromSaleOfRestrictedInvestments
Unrealized net (losses) gains on available-for-sale securities	$ (72)us-gaap_AvailableForSaleSecuritiesChangeInNetUnrealizedHoldingGainLossNetOfTax
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Maturity period of investments	One year or less

X

- Definition

Investment maturity period.

+ References

No definition available.

+ Details

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X

- Definition

The change in unrealized holding gain (loss), net of tax, on available-for-sale securities included in a separate component of shareholders' equity during the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 9

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563

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X

- Definition

The cash inflow associated with the sale of investments that are pledged or subject to withdrawal restrictions during the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585



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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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