Investments Available-for-Sale Securities in a Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	$ 55,822	$ 222,581
Less than 12 months, gross unrealized holding losses	232	2,502
12 Months or Longer, Estimated Fair Value	92,780	128,301
12 Months or Longer, Gross Unrealized Holding Losses	1,414	4,366
Total Estimated Fair Value	148,602	350,882
Total Gross Unrealized Holding Losses	(1,646)	(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	0	42,718
Less than 12 months, gross unrealized holding losses	0	440
12 Months or Longer, Estimated Fair Value	1,425	34,326
12 Months or Longer, Gross Unrealized Holding Losses	2	854
Total Estimated Fair Value	1,425	77,044
Total Gross Unrealized Holding Losses	(2)	(1,294)
Corporate and other securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	9,716	62,045
Less than 12 months, gross unrealized holding losses	29	890
12 Months or Longer, Estimated Fair Value	5,359	12,092
12 Months or Longer, Gross Unrealized Holding Losses	200	511
Total Estimated Fair Value	15,075	74,137
Total Gross Unrealized Holding Losses	(229)	(1,401)
Commercial mortgage and asset-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	41,047	93,247
Less than 12 months, gross unrealized holding losses	195	1,017
12 Months or Longer, Estimated Fair Value	32,809	25,746
12 Months or Longer, Gross Unrealized Holding Losses	290	505
Total Estimated Fair Value	73,856	118,993
Total Gross Unrealized Holding Losses	(485)	(1,522)
Residential mortgage-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Estimated Fair Value	5,059	24,571
Less than 12 months, gross unrealized holding losses	8	155
12 Months or Longer, Estimated Fair Value	53,187	55,638
12 Months or Longer, Gross Unrealized Holding Losses	922	2,495
Total Estimated Fair Value	58,246	80,209
Total Gross Unrealized Holding Losses	$ (930)	$ (2,650)