This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References+ Details

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).

+ References

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

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item 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 Company 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.

+ References+ Details

Fair Value of Financial Instruments Fair Value of Financial Instruments - Available-for-sale Securities (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	$ 508,119	$ 350,790	$ 279,588	$ 174,999
Available-for-sale Debt Securities - Cost	678,552	294,689
Commercial Paper [Member] \| Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	181,886	17,494
Commercial Paper [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Commercial Paper [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	181,886	17,494
Commercial Paper [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
US Government or Government Agencies [Member] \| Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	265,261	108,364
US Government or Government Agencies [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
US Government or Government Agencies [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	265,261	108,364
US Government or Government Agencies [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	0	0
Money Market Funds [Member] \| Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Schedule of Available-for-sale Securities [Line Items]
Money market funds - Fair Value		168,831
Fair Value, Measurements, Recurring [Member] \| Estimate of Fair Value, Fair Value Disclosure [Member]
Schedule of Available-for-sale Securities [Line Items]
Money market funds - Fair Value	231,417	168,831
Total Available-for-sale Debt Securities - Fair Value	678,564	294,689
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Money market funds - Fair Value	0	0
Total Available-for-sale Debt Securities - Fair Value	0	0
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Money market funds - Fair Value	231,417	168,831
Total Available-for-sale Debt Securities - Fair Value	678,564	294,689
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Schedule of Available-for-sale Securities [Line Items]
Money market funds - Fair Value	0	0
Total Available-for-sale Debt Securities - Fair Value	0	0
Fair Value, Measurements, Nonrecurring [Member]
Schedule of Available-for-sale Securities [Line Items]
Total Available-for-sale Debt Securities - Fair Value	0
US Government or Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities - Cost	265,251	108,364
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	231,417	168,831
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Debt Securities - Cost	$ 181,884	$ 17,494