Reinsurance (Details 4) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Amounts of letters of credit and cash deposits held by us as collateral, plus other credits available for potential offset
Payables to reinsurers	$ 195,806	$ 243,990
Letters of credit	120,589	145,914
Cash deposits	83,731	81,966
Total credits	$ 400,126	$ 471,870