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Concentration of Credit Risk and Fair Value of Financial Assets and Liabilities Fair Value of Financial Assets and Liabilities (Details) (USD $)
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Jun. 30, 2011
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Dec. 31, 2010
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Commercial Paper |
$ 12,000,000 |
|
|
|
| Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value |
22,000,000 |
|
|
|
| Long-term Debt |
188,822,000 |
|
180,000 |
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| Long-term Debt, Fair Value |
240,600,000 |
|
|
|
|
US Government and Government Agencies and Authorities [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
|
| Assets, Fair Value Disclosure, Recurring |
126,079,000 |
|
162,068,000 |
[1] |
|
US Government and Government Agencies and Authorities [Member] | Fair Value, Inputs, Level 1 [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
26,094,000 |
|
24,339,000 |
[1] |
|
US Government and Government Agencies and Authorities [Member] | Fair Value, Inputs, Level 2 [Member]
|
|
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
99,985,000 |
|
137,729,000 |
[1] |
|
US Government and Government Agencies and Authorities [Member] | Fair Value, Inputs, Level 3 [Member]
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|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
0 |
|
0 |
[1] |
|
Money Market Funds and Demand Deposits [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
379,589,000 |
[2] |
181,465,000 |
[2] |
|
Money Market Funds and Demand Deposits [Member] | Fair Value, Inputs, Level 1 [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
379,589,000 |
[2] |
181,465,000 |
[2] |
|
Money Market Funds and Demand Deposits [Member] | Fair Value, Inputs, Level 2 [Member]
|
|
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
[2] |
0 |
[2] |
|
Money Market Funds and Demand Deposits [Member] | Fair Value, Inputs, Level 3 [Member]
|
|
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
0 |
[2] |
0 |
[2] |
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Commercial Paper [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
170,848,000 |
|
175,394,000 |
[1] |
|
Commercial Paper [Member] | Fair Value, Inputs, Level 1 [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
12,011,000 |
|
15,541,000 |
[1] |
|
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
158,837,000 |
|
159,853,000 |
[1] |
|
Commercial Paper [Member] | Fair Value, Inputs, Level 3 [Member]
|
|
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
0 |
|
0 |
[1] |
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Corporate bonds [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
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|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
24,597,000 |
|
22,742,000 |
|
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Corporate bonds [Member] | Fair Value, Inputs, Level 1 [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
19,214,000 |
|
8,992,000 |
|
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Corporate bonds [Member] | Fair Value, Inputs, Level 2 [Member]
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|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
5,383,000 |
|
13,750,000 |
|
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Corporate bonds [Member] | Fair Value, Inputs, Level 3 [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
0 |
|
0 |
|
|
Estimate of Fair Value, Fair Value Disclosure [Member]
|
|
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
701,113,000 |
|
541,669,000 |
|
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Fair Value, Inputs, Level 1 [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
436,908,000 |
|
230,337,000 |
|
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Fair Value, Inputs, Level 2 [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
264,205,000 |
|
311,332,000 |
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Fair Value, Inputs, Level 3 [Member]
|
|
|
|
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
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| Assets, Fair Value Disclosure, Recurring |
$ 0 |
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$ 0 |
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