Investment In Securities - Weighted Average Lives of Trading Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value
Less than 1 year	$ 0	$ 0
Greater than or equal to 1 year and less than 3 years	649,425	389,883
Greater than or equal to 3 years and less than 5 years	1,522,509	407,656
Greater than or equal to 5 years	1,035,486	86,062
Total	3,207,420	883,601
Amortized Cost
Less than 1 year	0	0
Greater than or equal to 1 year and less than 3 years	650,328	369,600
Greater than or equal to 3 years and less than 5 years	1,506,035	375,030
Greater than or equal to 5 years	1,030,366	80,214
Amortized Cost	$ 3,186,729	$ 824,844