| 
           Related Party Transactions (Details 6) (USD $) 
        In Thousands, unless otherwise specified  | 
        12 Months Ended | |
|---|---|---|
| 
           Dec. 31, 2010 
         | 
        
           Dec. 31, 2009 
         | 
      |
| 
           GM [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | $ 48,257 | $ 130,394 | 
| 
           GM [Member] | Sales and marketing [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | 13,374 | 31,595 | 
| 
           GM [Member] | Revenue share and royalties [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | 15,823 | 58,992 | 
| 
           GM [Member] | Subscriber acquisition costs [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | 17,514 | 34,895 | 
| 
           GM [Member] | Customer service and billing [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | 125 | 268 | 
| 
           GM [Member] | Interest expense, net of amounts capitalized [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | 1,421 | 4,644 | 
| 
           American Honda [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | 5,136 | 12,438 | 
| 
           American Honda [Member] | Sales and marketing [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | 500 | |
| 
           American Honda [Member] | Revenue share and royalties [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | 3,167 | 6,541 | 
| 
           American Honda [Member] | Subscriber acquisition costs [Member] 
         | 
        ||
| Expenses incurred with General Motors Company and American Honda | ||
| Total | $ 1,969 | $ 5,397 |