Investments Investments (Available for Sale) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,521,792	$ 1,371,519
Gross Unrealized Holding Gains	6,170	30,307
Gross Unrealized Holding Losses	66,547	9,760
Estimated Fair Value	1,461,415	1,392,066
U.S. Treasury securities and obligations of U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,544	6,936
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	560	89
Estimated Fair Value	13,984	6,847
Obligations of states, municipalities and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	222,054	216,375
Gross Unrealized Holding Gains	2,611	12,139
Gross Unrealized Holding Losses	6,906	469
Estimated Fair Value	217,759	228,045
Corporate and other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	557,822	450,594
Gross Unrealized Holding Gains	2,312	11,714
Gross Unrealized Holding Losses	31,048	3,821
Estimated Fair Value	529,086	458,487
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	275,052	299,810
Gross Unrealized Holding Gains	789	2,217
Gross Unrealized Holding Losses	2,183	252
Estimated Fair Value	273,658	301,775
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	381,691	340,804
Gross Unrealized Holding Gains	332	1,804
Gross Unrealized Holding Losses	23,988	4,923
Estimated Fair Value	358,035	337,685
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	70,629	57,000
Gross Unrealized Holding Gains	126	2,433
Gross Unrealized Holding Losses	1,862	206
Estimated Fair Value	$ 68,893	$ 59,227