Investment Securities (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Cost
Equity	$ 259,356	$ 258,870
Debt	519,421	354,535
Other	10,564	6,356
Total	789,341	619,761
Gains
Equity	160,336	144,832
Debt	20,198	8,474
Other	0	0
Total	180,534	153,306
Losses
Equity	(11,785)	(5,990)
Debt	(940)	(874)
Other	(6)	0
Total	(12,731)	(6,864)
Fair Value
Equity	407,907	397,712
Debt	538,679	362,135
Other	10,558	6,356
Total	$ 957,144	$ 766,203