Schedule of Additional Information about Investments in Unrealized Loss Position (Detail)	Jun. 30, 2013	Dec. 31, 2012
Investments Debt And Equity Securities [Abstract]
Number of issues (Cusip numbers) held, Less than Twelve Months	447	195
Number of issues (Cusip numbers) held, Twelve Months or Longer	68	95
Number of issues (Cusip numbers) held, Total	515	290

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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