Schedule VI - Supplementary Information Concerning Property/Casualty Insurance Operations (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Losses and loss expenses incurred related to - current year	$ 3,513,469	$ 4,021,353	$ 4,081,376
Losses and loss expenses incurred related to - prior year	(255,076)	(289,889)	(315,894)
P&C Operations
Supplemental Information for Property, Casualty Insurance Underwriters [Line Items]
Deferred acquisition costs	357,067	537,473	536,664
Reserves for losses and loss expenses	19,353,241	20,481,065	20,484,121
Reserves for unearned premiums	3,973,159	3,846,568	3,755,117
Net earned premiums	5,717,438	6,014,099	5,765,978
Net investment income	642,492	671,071	712,905
Losses and loss expenses incurred related to - current year	3,513,469	4,021,353	4,081,376
Losses and loss expenses incurred related to - prior year	(255,076)	(289,889)	(315,894)
Net paid losses and loss expenses	3,821,335	3,828,139	3,783,242
Amortization of deferred acquisition costs	724,003	882,658	872,399
Net premiums written	$ 5,767,209	$ 5,903,982	$ 5,957,019