Commitments, Guarantees and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012
Loss Contingencies [Line Items]
Purchase obligations in 2013	124
Purchase obligations in 2014	83
Purchase obligations in 2015	26
Purchase obligations in 2016	13
Purchase obligations thereafter	16
New Tricare South Region Contract
Loss Contingencies [Line Items]
Contract term, years	5 years
Contract expiration date	Mar. 31, 2017
Puerto Rico Health Insurance Administration Contracts East Southeast And Southwest Regions
Loss Contingencies [Line Items]
Contract term, years	3 years
Contract expiration date	Jun. 30, 2013
Medicare
Loss Contingencies [Line Items]
Percentage of premiums and services revenue	72.00%
Military Services
Loss Contingencies [Line Items]
Percentage of premiums and services revenue	3.00%
Medicaid
Loss Contingencies [Line Items]
Percentage of premiums and services revenue	3.00%

Contract Expiration Date

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- Definition

Contract term, years.

+ References

No definition available.

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- Definition

Percentage Of Total Premium And Services Revenues

+ References

No definition available.

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 7

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the four fiscal year following the latest fiscal year.

+ References

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the second fiscal year following the latest fiscal year.

+ References

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the third fiscal year following the latest fiscal year.

+ References

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing after the fifth fiscal year following the latest fiscal year.

+ References

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