Investments Gross Unrealized Gains and Losses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	$ 1,293,853	$ 1,223,747
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	85,661	18,604
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,555	11,312
Debt Securities, Available-for-sale	1,377,959	1,231,039
US Treasury Securities [Member]
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	9,709	9,864
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,638	1,410
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt Securities, Available-for-sale	11,347	11,274
US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	3,516	3,540
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	1,015	740
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt Securities, Available-for-sale	4,531	4,280
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	512,239	713,991
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	24,285	7,614
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	240	1,490
Debt Securities, Available-for-sale	536,284	720,115
Corporate Debt Securities [Member]
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	604,750	384,817
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	46,472	6,725
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	1,134	9,746
Debt Securities, Available-for-sale	650,088	381,796
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	1,105	39,694
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	0	386
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	5	66
Debt Securities, Available-for-sale	1,100	40,014
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	118,130	66,960
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	12,223	1,726
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	66	2
Debt Securities, Available-for-sale	130,287	68,684
Asset-backed Securities [Member]
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	44,302	4,764
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	11	1
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	110	8
Debt Securities, Available-for-sale	44,203	4,757
Foreign Governments [Member]
Debt Securities, Available-for-Sale, Fair Value to Amortized Cost [Abstract]
Debt Securities, Available-for-sale, Amortized Cost	102	117
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax	17	2
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax	0	0
Debt Securities, Available-for-sale	$ 119	$ 119