Unpaid Losses and Loss Expenses and Policy Benefits for Life and Annuity Contracts Reconciliation of losses and loss expenses including life policy benefits (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of loss and loss expense
Losses and loss expenses and life policy benefits	$ 870,000	$ 960,000	$ 884,000	$ 749,000	$ 879,000	$ 751,000	$ 867,000	$ 661,000	$ 3,462,770	$ 3,157,808	$ 2,804,610
Non Life [Member]
Reconciliation of loss and loss expense
Losses and loss expenses and life policy benefits									2,462,568	2,397,256	2,157,629
Life and Health [Member]
Reconciliation of loss and loss expense
Losses and loss expenses and life policy benefits									$ 1,000,202	$ 760,552	$ 646,981