Investments Available-for-Sale Securities in a Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	$ 111,946	$ 222,581
Less than 12 months, gross unrealized holding losses	574	2,502
12 Months or Longer, Estimated Fair Value	75,066	128,301
12 Months or Longer, Gross Unrealized Holding Losses	923	4,366
Total Estimated Fair Value	187,012	350,882
Total Gross Unrealized Holding Losses	(1,497)	(6,868)
U.S. Treasury securities and obligations of U.S. government agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value		0
Less than 12 months, gross unrealized holding losses		0
12 Months or Longer, Estimated Fair Value		499
12 Months or Longer, Gross Unrealized Holding Losses		1
Total Estimated Fair Value		499
Total Gross Unrealized Holding Losses		(1)
Obligations of states, municipalities and political subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	12,993	42,718
Less than 12 months, gross unrealized holding losses	188	440
12 Months or Longer, Estimated Fair Value	256	34,326
12 Months or Longer, Gross Unrealized Holding Losses	1	854
Total Estimated Fair Value	13,249	77,044
Total Gross Unrealized Holding Losses	(189)	(1,294)
Corporate and other securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	22,122	62,045
Less than 12 months, gross unrealized holding losses	126	890
12 Months or Longer, Estimated Fair Value	5,232	12,092
12 Months or Longer, Gross Unrealized Holding Losses	68	511
Total Estimated Fair Value	27,354	74,137
Total Gross Unrealized Holding Losses	(194)	(1,401)
Commercial mortgage and asset-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	35,140	93,247
Less than 12 months, gross unrealized holding losses	130	1,017
12 Months or Longer, Estimated Fair Value	31,802	25,746
12 Months or Longer, Gross Unrealized Holding Losses	348	505
Total Estimated Fair Value	66,942	118,993
Total Gross Unrealized Holding Losses	(478)	(1,522)
Residential mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	41,691	24,571
Less than 12 months, gross unrealized holding losses	130	155
12 Months or Longer, Estimated Fair Value	37,776	55,638
12 Months or Longer, Gross Unrealized Holding Losses	506	2,495
Total Estimated Fair Value	79,467	80,209
Total Gross Unrealized Holding Losses	$ (636)	$ (2,650)