Reserves for Unpaid Losses and Loss Adjustment Expenses (Incurred and Paid Claims Development - Personal Segment) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) claim	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2008 USD ($)
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	$ 40,105	$ 7,608	$ (6,953)
Incurred claims and claim adjustment expenses related to current year	248,203	246,080	237,102
Total incurred	288,308	253,688	230,149
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	181,277	150,378	122,122
Paid claims and allocated claim adjustment expenses related to current year	92,873	93,067	83,132
Total paid	274,150	243,445	205,254
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	372,488	358,330	348,087	$ 323,192
Personal Segment [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Total incurred	482,690
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Total paid	471,182
All outstanding liabilities before 2007, net of reinsurance	(3)
Liabilities for unpaid claims and claim adjustment expenses, net of reinsurance	11,505
Personal Segment [Member] | Loss Adjustment Expenses Recognized In 2008 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	$ 40,401	40,369	40,324	40,239	$ 40,170	$ 39,793	$ 39,412	$ 38,329	$ 36,976	$ 36,247
Cumulative number of reported claims | claim	17,354
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 40,404	40,347	40,323	40,309	40,210	39,511	38,925	36,782	32,555	$ 20,005
Personal Segment [Member] | Loss Adjustment Expenses Recognized In 2009 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	$ 49,971	49,891	49,772	49,694	48,930	47,977	46,244	42,092	40,436
Cumulative number of reported claims | claim	21,054
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 49,957	49,853	49,704	49,539	49,287	47,967	44,689	37,621	$ 23,306
Personal Segment [Member] | Loss Adjustment Expenses Recognized In 2010 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	$ 84,808	84,591	84,252	83,903	84,724	80,765	78,294	63,862
Cumulative number of reported claims | claim	30,180
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 84,717	84,556	84,111	83,511	82,624	75,199	67,755	$ 38,643
Personal Segment [Member] | Loss Adjustment Expenses Recognized In 2011 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	$ 86,853	86,948	86,804	86,757	87,810	77,652	75,746
Cumulative number of reported claims | claim	31,614
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 86,660	86,593	86,217	85,533	83,497	67,939	$ 46,416
Personal Segment [Member] | Loss Adjustment Expenses Recognized In 2012 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	$ 72,037	72,042	71,513	70,552	73,795	58,604
Cumulative number of reported claims | claim	23,938
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 72,055	71,995	70,807	68,849	64,278	$ 37,860
Personal Segment [Member] | Loss Adjustment Expenses Recognized In 2013 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	60,379	60,211	60,100	59,132	55,706
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 69
Cumulative number of reported claims | claim	23,468
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 60,277	59,775	58,047	54,514	$ 45,901
Personal Segment [Member] | Loss Adjustment Expenses Recognized In 2014 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	6,699	6,243	5,340	5,452
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 239
Cumulative number of reported claims | claim	19,297
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 6,428	5,631	4,418	$ 2,515
Personal Segment [Member] | Loss Adjustment Expenses Recognized in 2015 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	25,307	25,682	23,104
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 642
Cumulative number of reported claims | claim	23,512
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 24,262	22,281	$ 11,570
Personal Segment [Member] | Loss Adjustment Expenses Recognized in 2016 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to prior years	32,893	32,260
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 1,309
Cumulative number of reported claims | claim	24,988
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to prior years	$ 30,646	$ 21,669
Personal Segment [Member] | Loss Adjustment Expenses Recognized in 2017 [Member]
Liability For Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract]
Incurred claims and claim adjustment expenses related to current year	23,342
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 4,253
Cumulative number of reported claims | claim	17,532
Liability For Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract]
Paid claims and allocated claim adjustment expenses related to current year	$ 15,776