SCHEDULE VI - Supplemental Information Concerning Property-Casualty Insurance Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Information Concerning Property-Casualty Insurance Operations [Line Items]
Unearned Premiums	$ 1,644,757	$ 1,750,607	$ 1,723,767
Premiums Earned	5,269,178	5,609,195	5,198,210
Losses and Loss Expenses Incurred	3,157,420	3,462,770	3,157,808
Premiums Written	4,343,345	4,765,907	4,556,765
Supplementary Insurance Information, Deferred Policy Acquisition Costs	629,372	661,186	644,952
Consolidated subsidiaries [Member]
Supplemental Information Concerning Property-Casualty Insurance Operations [Line Items]
Deferred Policy Acquisition Costs	449,216	463,958	434,111
Liability for Unpaid Losses and Loss Expenses	9,064,711	9,745,806	10,646,318
Unearned Premiums	1,629,537	1,731,212	1,699,430
Premiums Earned	4,059,665	4,387,444	4,241,064
Losses and Loss Expenses Incurred	2,192,999	2,462,568	2,397,256
Amortization of Deferred Policy Acquisition Costs	1,063,685	1,065,133	952,997
Paid Losses and Loss Expenses	2,422,603	2,798,549	2,401,559
Premiums Written	$ 4,022,067	$ 4,500,214	$ 4,432,829