Includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits are not generally reported as cash and cash equivalents. Includes cash and cash equivalents associated with the entity's continuing operations. Excludes cash and cash equivalents associated with the disposal group (and discontinued operation).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 1
-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 7
-Footnote 1
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3044-108585

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 8, 9
-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.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6361293&loc=d3e6676-107765

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash
-URI http://asc.fasb.org/extlink&oid=6506951

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 7, 26
-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.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Cash Equivalents
-URI http://asc.fasb.org/extlink&oid=6507016

+ Details

Organization and Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions	6 Months Ended				6 Months Ended							3 Months Ended					1 Months Ended	11 Months Ended	12 Months Ended		1 Months Ended	11 Months Ended	12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Dec. 31, 2009	Jun. 30, 2010 Overstatement	Mar. 31, 2011 Overstatement	Dec. 31, 2010 Overstatement	Dec. 31, 2009 Overstatement	Dec. 31, 2008 Overstatement	Jan. 31, 2008 Overstatement	Dec. 31, 2007 Overstatement	Mar. 31, 2011 Understatement	Dec. 31, 2010 Understatement	Dec. 31, 2008 Understatement	Jan. 31, 2008 Understatement	Dec. 31, 2007 Understatement	Jan. 31, 2008 Scenario, Previously Reported	Dec. 31, 2008 Scenario, Previously Reported	Dec. 31, 2010 Scenario, Previously Reported	Dec. 31, 2009 Scenario, Previously Reported	Jan. 31, 2008 Restated Amount	Dec. 31, 2008 Restated Amount	Dec. 31, 2010 Restated Amount	Dec. 31, 2009 Restated Amount
Cash and cash equivalents	$ 718	$ 997	$ 1,090	$ 888	$ 62	$ 47	$ 44	$ 59	$ 79	$ 50	$ 46
Marketable securities												47	44	79	50	46
Net cash flows provided by (used in) investing activities	$ (354)	$ 89			$ 3							$ 3					$ 77	$ (221)	$ 2	$ (98)	$ 74	$ (250)	$ 17	$ (78)
Description of prior period reclassification adjustment	During the second quarter of 2011, we determined that marketable securities having original maturities greater than 90 days had been incorrectly reported as cash and cash equivalents in prior periods. As a result, there was an overstatement of cash and cash equivalents and understatement of marketable securities of $44 at December 31, 2010 and of $47 at March 31, 2011 and an understatement of $3 in cash used in investing activities for the three months ended March 31, 2011. With respect to the amounts reported for the six months ended June 30, 2010, the $59 overstatement of December 31, 2009 cash and cash equivalents increased to $62 during the period, causing a $3 overstatement of cash flows provided by investing activities. In our 2010 Form 10-K, the cash and cash equivalents reported as of December 31, 2007 and 2008 and January 31, 2008 were overstated by $46, $79 and $50 with corresponding understatements of marketable securities. As a result, the reported cash provided by (used in) investing activities for the one month ended January 31, 2008, the eleven months ended December 31, 2008 and the years ended December 31, 2009 and 2010 of $77, $(221), $(98) and $2 should have been $74, $(250), $(78) and $17. Amounts reported in prior periods have been revised in the accompanying financial statements and the related notes. These revisions were not considered material to the current period or to the prior periods to which they relate.