Liability for Unpaid Loss and Loss Adjustment Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNetAbstract
Reserves at beginning of period	$ 3,692,522	$ 3,847,417	$ 3,728,085	$ 3,902,132
Less reinsurance recoverables on reserves	1,082,484	1,098,576	1,070,463	1,122,731
Net reserves at beginning of period	2,610,038	2,748,841	2,657,622	2,779,401
Net reserve additions from acquired business	0		8,743
Net loss and loss adjustment expense:
Net loss and loss adjustment expense	395,305	335,897	760,467	666,643
Net loss and loss adjustment expense payments for claims occurring during:
Net loss and loss adjustment expense payments	(431,975)	(327,917)	(820,513)	(691,775)
Foreign currency adjustment	13,306	3,427	(19,645)	5,979
Net reserves at end of period	2,586,674	2,760,248	2,586,674	2,760,248
Plus reinsurance recoverables on reserves	1,073,814	1,081,249	1,073,814	1,081,249
Reserves at end of period	$ 3,660,488	$ 3,841,497	$ 3,660,488	$ 3,841,497