Investments (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) security	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) security	Sep. 30, 2020 USD ($)	Dec. 31, 2020 security
Schedule of Available-for-sale Securities [Line Items]
Gross gains on investments	$ 1,100	$ 500	$ 5,800	$ 22,400
Gross losses on investments	0	100	500	16,800
Proceeds from sale of investment securities	$ 1,100	47,400	16,900	155,000
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Gain on debt securities			600	0
Other-than-temporary impairment		$ 1,692	$ 0	$ 1,692
Debt Securities [Member]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Number of debt securities with unrealized loss | security	86		86		81
Number of debt securities with unrealized loss, less than 12 months | security	58		58		64
Number of debt securities with unrealized loss, greater than 12 months | security	28		28		17