Policy and Claim Reserves (Property and Casualty Reserve) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Less reinsurance recoverable on unpaid losses	$ 503		$ 1,780
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Estimated claims and claim adjustment expenses for claims arising in prior years	(1,355)	$ (1,673)
Consolidated Property and Casualty Insurance Entity
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Policy and contract claims	8,897	7,433	7,531	$ 9,645
Less reinsurance recoverable on unpaid losses	354	427	1,184	1,380
Net balances at beginning of year	8,543	7,006	$ 6,347	$ 8,265
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Provision for claims and claim adjustment expenses for claims arising in current year	32,867	25,987
Estimated claims and claim adjustment expenses for claims arising in prior years	(1,355)	(1,673)
Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims	31,512	24,314
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year	26,275	20,923
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years	3,041	4,650
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid	$ 29,316	$ 25,573