Investment Securities - Allowance for Credit Loss Rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Jan. 01, 2020
Debt Securities, Available-for-sale [Line Items]
Adjustment to initially apply ASU No. 2016-13 for CECL	$ 869
Securities, available-for-sale, allowance for credit loss, ending balance	869
Corporate Bonds [Member]
Debt Securities, Available-for-sale [Line Items]
Securities, available-for-sale, allowance for credit loss, beginning balance	0
Adjustment to initially apply ASU No. 2016-13 for CECL	869	$ 0
Change in securities for which a previous expected credit loss was recognized	(569)
Securities, available-for-sale, allowance for credit loss, ending balance	$ 869
Corporate Bonds [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Debt Securities, Available-for-sale [Line Items]
Adjustment to initially apply ASU No. 2016-13 for CECL		$ 300