Reinsurance and Policy Benefits and Losses, Claims, and Loss Expenses Payable (Incurred Claims Development) (Details) $ in Thousands	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Incurred claims development [Abstract]
Shortduration Insurance Contracts Incurred But Not Reported Ibnr Claims Liability Net	$ 8,212
Accident Year 2012 [Member] | Property and Casualty Insurance [Member]
Incurred claims development [Abstract]
Shortduration Insurance Contracts Incurred Claims And Allocated Claim Adjustment Expense Net	8,735	$ 8,753	$ 8,788	$ 8,831	$ 8,903	$ 8,971
Shortduration Insurance Contracts Incurred But Not Reported Ibnr Claims Liability Net
Shortduration Insurance Contracts Number Of Reported Claims	6,889
Accident Year 2013 [Member] | Property and Casualty Insurance [Member]
Incurred claims development [Abstract]
Shortduration Insurance Contracts Incurred Claims And Allocated Claim Adjustment Expense Net	$ 9,576	9,741	9,914	9,853	$ 9,861
Shortduration Insurance Contracts Incurred But Not Reported Ibnr Claims Liability Net
Shortduration Insurance Contracts Number Of Reported Claims	7,663
Accident Year 2014 [Member] | Property and Casualty Insurance [Member]
Incurred claims development [Abstract]
Shortduration Insurance Contracts Incurred Claims And Allocated Claim Adjustment Expense Net	$ 10,759	10,720	10,907	$ 11,691
Shortduration Insurance Contracts Incurred But Not Reported Ibnr Claims Liability Net	$ 374
Shortduration Insurance Contracts Number Of Reported Claims	9,648
Accident Year 2015 [Member] | Property and Casualty Insurance [Member]
Incurred claims development [Abstract]
Shortduration Insurance Contracts Incurred Claims And Allocated Claim Adjustment Expense Net	$ 12,460	12,459	$ 12,214
Shortduration Insurance Contracts Incurred But Not Reported Ibnr Claims Liability Net	$ 1,649
Shortduration Insurance Contracts Number Of Reported Claims	10,718
Accident Year 2016 [Member] | Property and Casualty Insurance [Member]
Incurred claims development [Abstract]
Shortduration Insurance Contracts Incurred Claims And Allocated Claim Adjustment Expense Net	$ 13,011	$ 13,297
Shortduration Insurance Contracts Incurred But Not Reported Ibnr Claims Liability Net	$ 1,366
Shortduration Insurance Contracts Number Of Reported Claims	11,134
Accident Year 2017 [Member] | Property and Casualty Insurance [Member]
Incurred claims development [Abstract]
Shortduration Insurance Contracts Incurred Claims And Allocated Claim Adjustment Expense Net	$ 15,749
Shortduration Insurance Contracts Incurred But Not Reported Ibnr Claims Liability Net	$ 4,823
Shortduration Insurance Contracts Number Of Reported Claims	11,424