Fair Value Measurements (Schedule of Fair Value Measurement) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Assets
Available-for-sale securities	$ 893,251	$ 670,758
Total Fair Value [Member]
Assets
Assets, fair value	921,879	1,030,763
Liabilities
Liabilities, fair value	(1,200)
Total Fair Value [Member] \| Money Market Funds [Member]
Assets
Cash equivalents	22,255	302,507
Total Fair Value [Member] \| Certificates of Deposit [Member]
Assets
Available-for-sale securities	7,473	42
Total Fair Value [Member] \| Commercial Paper [Member]
Assets
Available-for-sale securities	9,482	57,498
Total Fair Value [Member] \| U.S. Government Agencies Obligations [Member]
Assets
Available-for-sale securities	189,674	145,908
Total Fair Value [Member] \| Corporate Debt Securities [Member]
Assets
Available-for-sale securities	692,995	524,808
Total Fair Value [Member] \| Contingent Consideration [Member]
Liabilities
Contingent consideration obligation related to Verivue acquisition	(1,200)
Level 1 [Member]
Assets
Assets, fair value	29,728	302,549
Liabilities
Liabilities, fair value	0
Level 1 [Member] \| Money Market Funds [Member]
Assets
Cash equivalents	22,255	302,507
Level 1 [Member] \| Certificates of Deposit [Member]
Assets
Available-for-sale securities	7,473	42
Level 1 [Member] \| Commercial Paper [Member]
Assets
Available-for-sale securities	0	0
Level 1 [Member] \| U.S. Government Agencies Obligations [Member]
Assets
Available-for-sale securities	0	0
Level 1 [Member] \| Corporate Debt Securities [Member]
Assets
Available-for-sale securities	0	0
Level 1 [Member] \| Contingent Consideration [Member]
Liabilities
Contingent consideration obligation related to Verivue acquisition	0
Level 2 [Member]
Assets
Assets, fair value	892,151	728,214
Liabilities
Liabilities, fair value	0
Level 2 [Member] \| Money Market Funds [Member]
Assets
Cash equivalents	0	0
Level 2 [Member] \| Certificates of Deposit [Member]
Assets
Available-for-sale securities	0	0
Level 2 [Member] \| Commercial Paper [Member]
Assets
Available-for-sale securities	9,482	57,498
Level 2 [Member] \| U.S. Government Agencies Obligations [Member]
Assets
Available-for-sale securities	189,674	145,908
Level 2 [Member] \| Corporate Debt Securities [Member]
Assets
Available-for-sale securities	692,995	524,808
Level 2 [Member] \| Contingent Consideration [Member]
Liabilities
Contingent consideration obligation related to Verivue acquisition	0
Level 3 [Member]
Assets
Assets, fair value	0	0
Liabilities
Liabilities, fair value	(1,200)
Level 3 [Member] \| Money Market Funds [Member]
Assets
Cash equivalents	0	0
Level 3 [Member] \| Certificates of Deposit [Member]
Assets
Available-for-sale securities	0	0
Level 3 [Member] \| Commercial Paper [Member]
Assets
Available-for-sale securities	0	0
Level 3 [Member] \| U.S. Government Agencies Obligations [Member]
Assets
Available-for-sale securities	0	0
Level 3 [Member] \| Corporate Debt Securities [Member]
Assets
Available-for-sale securities	0	0
Level 3 [Member] \| Contingent Consideration [Member]
Liabilities
Contingent consideration obligation related to Verivue acquisition	$ (1,200)

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.

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Fair value, as of the acquisition date, of potential payments under the contingent consideration arrangement including cash and shares.

+ References

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+ 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.

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