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Fair Value Measurements - Summary of Changes in Fair Value of Assets Measured at Fair Value (Detail) (Fair Value, Inputs, Level 3 [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Fair Value, Inputs, Level 3 [Member]
Fair Value Measurements Disclosure [Line Items]
Beginning balance
Purchases	10,000
Total gains unrealized (Included in earnings as part of net investment income)	271
Ending balance	$ 10,271

X

- Definition

Fair Value Assets Measured On Recurring Basis Change In Unrealized Gain Loss Included In Earnings

+ References

No definition available.

+ Details

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X

- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

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X

- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258

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