|
Summary of Significant Accounting Policies Fair Value Measurements (Details) (USD $)
|
12 Months Ended |
|
Dec. 31, 2011
|
Dec. 31, 2010
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Concentration Risk, Additional Characteristic |
three |
four |
| Concentration Risk, Percentage |
97.00% |
92.00% |
| Assets, Fair Value Disclosure, Recurring |
$ 677,994,000 |
$ 541,669,000 |
| Commercial Paper |
4,000,000 |
12,000,000 |
| Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value |
|
22,000,000 |
| Long-term Debt, Excluding Current Maturities |
192,529,000 |
180,000 |
| Long-term Debt, Fair Value |
240,900,000 |
|
|
Money Market Funds and Demand Deposits [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
338,211,000 |
181,465,000 |
|
Mutual and Exchange Traded Funds [Domain]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
96,130,000 |
|
|
Commercial Paper [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
160,574,000 |
175,394,000 |
|
US Government and Government Agencies and Authorities [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
66,647,000 |
162,068,000 |
|
Corporate Bonds and Asset Backed Securities [Domain]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
16,432,000 |
|
|
Corporate Bond Securities [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
|
22,742,000 |
|
Fair Value, Inputs, Level 1 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
434,341,000 |
181,465,000 |
|
Fair Value, Inputs, Level 1 [Member] | Money Market Funds and Demand Deposits [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
338,211,000 |
181,465,000 |
|
Fair Value, Inputs, Level 1 [Member] | Mutual and Exchange Traded Funds [Domain]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
96,130,000 |
|
|
Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
0 |
|
Fair Value, Inputs, Level 1 [Member] | US Government and Government Agencies and Authorities [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
0 |
|
Fair Value, Inputs, Level 1 [Member] | Corporate Bonds and Asset Backed Securities [Domain]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
|
|
Fair Value, Inputs, Level 1 [Member] | Corporate Bond Securities [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
|
0 |
|
Fair Value, Inputs, Level 2 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
243,653,000 |
360,204,000 |
|
Fair Value, Inputs, Level 2 [Member] | Money Market Funds and Demand Deposits [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
0 |
|
Fair Value, Inputs, Level 2 [Member] | Mutual and Exchange Traded Funds [Domain]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
|
|
Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
160,574,000 |
175,394,000 |
|
Fair Value, Inputs, Level 2 [Member] | US Government and Government Agencies and Authorities [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
66,647,000 |
162,068,000 |
|
Fair Value, Inputs, Level 2 [Member] | Corporate Bonds and Asset Backed Securities [Domain]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
16,432,000 |
|
|
Fair Value, Inputs, Level 2 [Member] | Corporate Bond Securities [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
|
22,742,000 |
|
Fair Value, Inputs, Level 3 [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
0 |
|
Fair Value, Inputs, Level 3 [Member] | Money Market Funds and Demand Deposits [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
0 |
|
Fair Value, Inputs, Level 3 [Member] | Mutual and Exchange Traded Funds [Domain]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
|
|
Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
0 |
|
Fair Value, Inputs, Level 3 [Member] | US Government and Government Agencies and Authorities [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
0 |
|
Fair Value, Inputs, Level 3 [Member] | Corporate Bonds and Asset Backed Securities [Domain]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
0 |
|
|
Fair Value, Inputs, Level 3 [Member] | Corporate Bond Securities [Member]
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
| Assets, Fair Value Disclosure, Recurring |
|
$ 0 |