Investments, Securities with Continuous Unrealized Loss Position (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) Securities	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($) Securities
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	$ 31,978		$ 11,647
12 months or longer	0		0
Total	31,978		11,647
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	1,111		94
12 months or longer	0		0
Total	1,111		$ 94
Gross OTTI losses charged to realized gains	$ 0	$ 0
Number of securities in unrealized loss position | Securities	37		20
U.S. Treasury Securities and Obligations of U.S. Government Agencies and Authorities [Member]
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	$ 12,883		$ 7,045
12 months or longer	0		0
Total	12,883		7,045
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	260		26
12 months or longer	0		0
Total	260		26
Corporate Securities [Member]
Available-for-sale securities, continuous unrealized loss position, Fair Value [Abstract]
Less than 12 months	19,095		4,602
12 months or longer	0		0
Total	19,095		4,602
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses [Abstract]
Less than 12 months	851		68
12 months or longer	0		0
Total	$ 851		$ 68