|
Concentration of Credit Risk and Fair Value of Financial Assets and Liabilities Fair Value of Financial Assets and Liabilities (Details) (USD $)
|
6 Months Ended |
|
|
Jun. 30, 2013
|
Jun. 30, 2012
|
Dec. 31, 2012
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
|
|
| Assets, Fair Value Disclosure, Recurring |
$ 769,792,000 |
|
|
$ 577,279,000 |
|
| Commercial Paper |
14,500,000 |
|
|
87,900,000 |
|
| LONG-TERM DEBT |
204,500,000 |
|
|
200,400,000 |
|
| LONG-TERM DEBT |
204,530,000 |
|
|
200,391,000 |
|
| Long-term Debt, Fair Value |
247,000,000 |
|
|
245,200,000 |
|
| Other than Temporary Impairment Losses, Investments |
6,669,000 |
|
0 |
|
|
| Investment Owned, at Fair Value |
15,100,000 |
|
|
|
|
|
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 |
444,548,000 |
[1] |
|
261,899,000 |
[1] |
|
Mutual and Exchange Traded Funds [Domain]
|
|
|
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
|
|
| Assets, Fair Value Disclosure, Recurring |
100,552,000 |
|
|
100,682,000 |
|
|
Commercial Paper [Member]
|
|
|
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
|
|
| Assets, Fair Value Disclosure, Recurring |
163,277,000 |
|
|
150,868,000 |
|
|
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 |
48,600,000 |
|
|
50,560,000 |
|
|
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 |
12,815,000 |
|
|
13,270,000 |
|
|
Fair Value, Inputs, Level 1 [Member]
|
|
|
|
|
|
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
|
|
|
|
| Assets, Fair Value Disclosure, Recurring |
545,100,000 |
|
|
362,581,000 |
|
|
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 |
444,548,000 |
|
|
261,899,000 |
|
|
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 |
100,552,000 |
|
|
100,682,000 |
|
|
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 |
|
|
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 |
224,692,000 |
|
|
214,698,000 |
|
|
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 |
|
|
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 |
163,277,000 |
|
|
150,868,000 |
|
|
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 |
12,815,000 |
|
|
13,270,000 |
|
|
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 |
|
|
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 |
|
|
$ 0 |
|
|
|
|