| Marketable Securities (Continuous Unrealized Loss Position) (Details) (USD $) | 3 Months Ended | 6 Months Ended | ||||||
|---|---|---|---|---|---|---|---|---|
| Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2012 | Dec. 31, 2011 | |||||
| Investments in an Unrealized Loss Position | ||||||||
| Fair Value | $ 274,107,000 | $ 274,107,000 | ||||||
| Gross Unrealized Losses, less than 12 months | (436,000) | [1] | (436,000) | [1] | ||||
| Continuous loss position not exceeding this period | 12 months | |||||||
| Net realized securities gains (losses) | 1,000,000 | (100,000) | 1,400,000 | 600,000 | ||||
| U.S. Treasury securities | ||||||||
| Investments in an Unrealized Loss Position | ||||||||
| Fair Value | 4,999,000 | 4,999,000 | ||||||
| Gross Unrealized Losses, less than 12 months | (3,000) | [1] | (3,000) | [1] | ||||
| U.S. Government agency securities | ||||||||
| Investments in an Unrealized Loss Position | ||||||||
| Fair Value | 37,083,000 | 37,083,000 | ||||||
| Gross Unrealized Losses, less than 12 months | (6,000) | [1] | (6,000) | [1] | ||||
| Municipal securities | ||||||||
| Investments in an Unrealized Loss Position | ||||||||
| Fair Value | 30,399,000 | 30,399,000 | ||||||
| Gross Unrealized Losses, less than 12 months | (88,000) | [1] | (88,000) | [1] | ||||
| Corporate debt securities | ||||||||
| Investments in an Unrealized Loss Position | ||||||||
| Fair Value | 200,660,000 | 200,660,000 | ||||||
| Gross Unrealized Losses, less than 12 months | (336,000) | [1] | (336,000) | [1] | ||||
| Sovereign securities | ||||||||
| Investments in an Unrealized Loss Position | ||||||||
| Fair Value | 966,000 | 966,000 | ||||||
| Gross Unrealized Losses, less than 12 months | $ (3,000) | [1] | $ (3,000) | [1] | ||||
| 
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