Investments (Details) (USD $)
| 3 Months Ended | 9 Months Ended | |
|---|
Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011 | Sep. 30, 2010 | Dec. 31, 2010 |
|---|
| Schedule of Available-for-sale Securities [Line Items] | | | | | |
| Cost or Amortized Cost | $ 9,150,000 | | $ 9,150,000 | | $ 9,150,000 |
| Net Unrealized Gain (Loss) | 550,000 | | 550,000 | | (550,000) |
| Changes in fair value of investments [Roll Forward] | | | | | |
| Fair value at beginning of period | 9,700,000 | 12,600,000 | 8,600,000 | 13,100,000 | |
| Temporary impairment (charges) credits, net | 0 | 250,000 | 1,100,000 | (250,000) | |
| Other-than-temporary impairment charges | | (850,000) | | (850,000) | |
| Sale of security | | (3,400,000) | | (3,400,000) | |
| Fair value at end of period | 9,700,000 | 8,600,000 | 9,700,000 | 8,600,000 | |
Debt Securities [Member] | | | | | |
| Schedule of Available-for-sale Securities [Line Items] | | | | | |
| Cost or Amortized Cost | 7,150,000 | | 7,150,000 | | 7,150,000 |
| Net Unrealized Gain (Loss) | 50,000 | | 50,000 | | (450,000) |
| Changes in fair value of investments [Roll Forward] | | | | | |
| Fair value at beginning of period | 6,900,000 | 10,500,000 | 6,700,000 | 10,900,000 | |
| Net change in fair value | 300,000 | (4,000,000) | 500,000 | (4,400,000) | |
| Temporary impairment (charges) credits, net | 300,000 | 250,000 | 500,000 | (150,000) | |
| Other-than-temporary impairment charges | | (850,000) | | (850,000) | |
| Sale of security | | (3,400,000) | | (3,400,000) | |
| Fair value at end of period | 7,200,000 | 6,500,000 | 7,200,000 | 6,500,000 | |
| Gain (Loss) from sale of security | | 900,000 | | | |
| Proceeds from sale of investments | | 4,300,000 | | | |
Equity Securities [Member] | | | | | |
| Schedule of Available-for-sale Securities [Line Items] | | | | | |
| Cost or Amortized Cost | 2,000,000 | | 2,000,000 | | 2,000,000 |
| Net Unrealized Gain (Loss) | 500,000 | | 500,000 | | (100,000) |
| Changes in fair value of investments [Roll Forward] | | | | | |
| Fair value at beginning of period | 2,800,000 | 2,100,000 | 1,900,000 | 2,200,000 | |
| Temporary impairment (charges) credits, net | (300,000) | 0 | 600,000 | (100,000) | |
| Fair value at end of period | 2,500,000 | 2,100,000 | 2,500,000 | 2,100,000 | |
Preferred Stock Investments [Member] | | | | | |
| Schedule of Available-for-sale Securities [Line Items] | | | | | |
| Cost or Amortized Cost | 0 | | 0 | | 0 |
| Changes in fair value of investments [Roll Forward] | | | | | |
| Fair value at beginning of period | | | | | 0 |
| Fair value at end of period | $ 0 | | $ 0 | | $ 0 |