Summary of Significant Accounting Policies (Detail) (C Corporation, USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Aug. 31, 2007
C Corporation
Acquisition of C corporation
Period over which gain on disposition of property recognized	10 years
Percentage of voting stock acquired		100.00%
Built-in gains on transfer of property	$ 59

Represents the recognition period of gain (loss) on disposition of property.

No definition available.

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- Details

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Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

+ Details

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Period Type:	instant

- Definition

Amount of gain on the sale of property that does not qualify for gain recognition as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 40

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.U.Q2)

-URI http://asc.fasb.org/extlink&oid=6955272&loc=d3e221323-122791

+ Details

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Period Type:	instant