Liability for Unpaid Loss and Loss Adjustment Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNetAbstract
Reserves at beginning of period	$ 3,847,417	$ 3,774,162	$ 3,902,132	$ 3,767,850
Less reinsurance recoverables on reserves	1,098,576	1,012,920	1,122,731	1,018,047
Net reserves at beginning of period	2,748,841	2,761,242	2,779,401	2,749,803
Net loss and loss adjustment expense:
Net loss and loss adjustment expense	327,094	339,474	648,938	672,171
Net loss and loss adjustment expense payments for claims occurring during:
Net loss and loss adjustment expense payments	(319,114)	(286,797)	(674,070)	(586,326)
Foreign currency adjustment	3,427	(2,898)	5,979	(24,627)
Net reserves at end of period	2,760,248	2,811,021	2,760,248	2,811,021
Plus reinsurance recoverables on reserves	1,081,249	1,003,663	1,081,249	1,003,663
Reserves at end of period	$ 3,841,497	$ 3,814,684	$ 3,841,497	$ 3,814,684