| Breakdown of gross and net premiums written and earned [Table Text Block] |
| Gross and net premiums written and earned were as follows: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Year ended December 31, | | 2011 | | 2010 | | 2009 | | | | | | Premiums | | Premiums | | Premiums | | | Premiums | | Premiums | | Premiums | | | | | | written | | earned | | written | | | earned | | written | | earned | | | | | | | | | | | | | | | | | | | | | | | | | | Gross | | $ | 4,096,153 | | $ | 3,973,956 | | $ | 3,750,536 | | $ | 3,632,177 | | $ | 3,587,295 | | $ | 3,540,298 | | | | Ceded | | | (676,719) | | | (658,995) | | | (602,996) | | | (684,767) | | | (770,866) | | | (748,534) | | | | Net | | $ | 3,419,434 | | $ | 3,314,961 | | $ | 3,147,540 | | $ | 2,947,410 | | $ | 2,816,429 | | $ | 2,791,764 | | | | | | | | | | | | | | | | | | | | | | | |
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