Investments Assessment for Credit Impairment (Details)	3 Months Ended
	Mar. 31, 2020 USD ($) security	Mar. 31, 2019 USD ($)
Investments [Abstract]
Past due held-to-maturity securities	$ 0
Credit allowance, held-to-maturity investment portfolio	$ 0
Number of available-for-sale securities with impairment | security	0
Credit allowance, available-for-sale investment portfolio	$ 0
Sales of equity securities	$ 0	$ 0