Reserves For Losses And Loss Expenses (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reserves For Losses And Loss Expenses [Line Items]
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims, Prior Years, Reserve Development, Net of Premiums, Favorable (Unfavorable)	$ 63,000	$ 85,000	$ 98,000
Prior year	2,342,378	2,216,283	2,055,284
Favorable Reserve Development Net Of Premium Offsets	63,000	85,000	98,000
Reserve for losses and loss adjustment expenses relating to asbestos and environmental claims, net	33,000	36,000
Reserve for losses and loss adjustment expenses relating to asbestos and environmental claims, gross	51,000	56,000
Increase (decrease) in net incurred losses and loss expenses relating to asbestos and environmental claims	2,000	4,000	5,000
Net paid losses and loss expenses for asbestos and environmental claims	2,000	3,000	3,000
Undiscounted [Member]
Reserves For Losses And Loss Expenses [Line Items]
Liability For Unpaid Claims And Claims Adjustment Expense Incurred Claims Undiscounted Basis Prior Years	30,000
Discounted [Member]
Reserves For Losses And Loss Expenses [Line Items]
Prior year	12,000
Insurance-Domestic
Reserves For Losses And Loss Expenses [Line Items]
Favorable Reserve Development Net Of Premium Offsets	47,000	92,000
Insurance-Domestic | Other Insurance Liabilities [Member]
Reserves For Losses And Loss Expenses [Line Items]
Favorable Reserve Development Net Of Premium Offsets			39,000
Insurance-Domestic | Workers' Compensation [Member]
Reserves For Losses And Loss Expenses [Line Items]
Favorable Reserve Development Net Of Premium Offsets			22,000
Insurance-Domestic | Property Insurance Product Line [Member]
Reserves For Losses And Loss Expenses [Line Items]
Favorable Reserve Development Net Of Premium Offsets			18,000
Insurance-Domestic | Other Insurance Product Line [Member]
Reserves For Losses And Loss Expenses [Line Items]
Favorable Reserve Development Net Of Premium Offsets			24,000
Insurance-Domestic | Commercial Automobile [Member]
Reserves For Losses And Loss Expenses [Line Items]
reserve development unfavorable			23,000
Insurance-Domestic | Products Liability
Reserves For Losses And Loss Expenses [Line Items]
reserve development unfavorable			14,000
Reinsurance-Global
Reserves For Losses And Loss Expenses [Line Items]
Favorable Reserve Development Net Of Premium Offsets	11,000	16,000
Reinsurance-Global | Assumed Business [Member]
Reserves For Losses And Loss Expenses [Line Items]
Favorable Reserve Development Net Of Premium Offsets			$ 32,000
Insurance-International
Reserves For Losses And Loss Expenses [Line Items]
Favorable Reserve Development Net Of Premium Offsets	$ 5,000
Adverse Reserve Development		$ 23,000