Restricted Investments, Held-to-Maturity (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2020 USD ($) Securities	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) Securities
Schedule of Investments [Line Items]
Cost or Amortized Cost	[1]	$ 8,836		$ 8,912
Gross Unrealized Gains		1		4
Gross Unrealized Temporary Losses		(31)		(1)
Estimated Fair Value	[1]	$ 8,806		$ 8,915
Securities with unrealized losses for less than 12 months | Securities		12		7
Impairment losses		$ 0	$ 0
US corporate securities [Member]
Schedule of Investments [Line Items]
Cost or Amortized Cost		8,836		$ 8,912
Gross Unrealized Gains		1		4
Gross Unrealized Temporary Losses		(31)		(1)
Estimated Fair Value		$ 8,806		$ 8,915
Maximum [Member]
Schedule of Investments [Line Items]
Contractual maturities of fixed maturity securities		1 year
Duration of securities in unrealized loss position		12 months

[1] Refer to Note 5 for the differences between the carrying amounts and estimated fair values of the Company's restricted investments, held-to-maturity.