Fair Value Measurements (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Trading securities:
Equity mutual funds	$ 613	$ 491
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Cash and cash equivalents	77,545	51,823
Trading securities:
Derivatives - currency forward contracts	0	0
Short-term investments	308,377	253,741
Long-term marketable securities	9,260
Other current assets, fair value	0	0
Total assets	395,182	305,564
Liabilities:
Derivatives - currency forward contracts	0
Other liabilities, fair value disclosure	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Available-for-sale securities:
Cash and cash equivalents	75,794	7,032
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Time deposits and drafts [Member]
Available-for-sale securities:
Cash and cash equivalents	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | Equity mutual funds [Member]
Trading securities:
Equity mutual funds	613	491
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member] | U.S. treasury and agency obligations [Member]
Available-for-sale securities:
U.S. treasury and agency obligations	318,775	298,041
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Cash and cash equivalents	30,888	2,838
Trading securities:
Derivatives - currency forward contracts	909	369
Short-term investments	1,351	15,716
Long-term marketable securities	0
Other current assets, fair value	909	369
Total assets	33,148	18,923
Liabilities:
Derivatives - currency forward contracts	2,074	3,463
Other liabilities, fair value disclosure	2,074	3,463
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Available-for-sale securities:
Cash and cash equivalents	0	0
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Time deposits and drafts [Member]
Available-for-sale securities:
Cash and cash equivalents	32,239	18,554
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | Equity mutual funds [Member]
Trading securities:
Equity mutual funds	0	0
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member] | U.S. treasury and agency obligations [Member]
Available-for-sale securities:
U.S. treasury and agency obligations	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Cash and cash equivalents	0	0
Trading securities:
Derivatives - currency forward contracts	0	0
Short-term investments	0	0
Long-term marketable securities	0
Other current assets, fair value	0	0
Total assets	0	0
Liabilities:
Derivatives - currency forward contracts	0
Other liabilities, fair value disclosure	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Available-for-sale securities:
Cash and cash equivalents	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Time deposits and drafts [Member]
Available-for-sale securities:
Cash and cash equivalents	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | Equity mutual funds [Member]
Trading securities:
Equity mutual funds	0	0
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member] | U.S. treasury and agency obligations [Member]
Available-for-sale securities:
U.S. treasury and agency obligations	0	0
Fair Value, Measurements, Recurring [Member]
Available-for-sale securities:
Cash and cash equivalents	108,433	54,661
Trading securities:
Derivatives - currency forward contracts	909	369
Short-term investments	309,728	269,457
Long-term marketable securities	9,260
Other current assets, fair value	909	369
Total assets	428,330	324,487
Liabilities:
Derivatives - currency forward contracts	2,074	3,463
Other liabilities, fair value disclosure	2,074	3,463
Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Available-for-sale securities:
Cash and cash equivalents	75,794	7,032
Fair Value, Measurements, Recurring [Member] | Time deposits and drafts [Member]
Available-for-sale securities:
Cash and cash equivalents	32,239	18,554
Fair Value, Measurements, Recurring [Member] | Equity mutual funds [Member]
Trading securities:
Equity mutual funds	613	491
Fair Value, Measurements, Recurring [Member] | U.S. treasury and agency obligations [Member]
Available-for-sale securities:
U.S. treasury and agency obligations	$ 318,775	$ 298,041