Investments - Schedule of Unrealized Loss on Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 82,145	$ 255,984
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	587	1,319
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	41,491
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	435
Debt Securities, Available-for-sale, Unrealized Loss Position	82,145	297,475
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	587	1,754
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	57,934	56,327
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	539	363
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	57,934	56,327
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	539	363
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	21,211	131,693
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	46	756
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	41,491
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	435
Debt Securities, Available-for-sale, Unrealized Loss Position	21,211	173,184
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	46	1,191
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	3,000	67,964
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2	200
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position	3,000	67,964
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 2	$ 200