Investments In Securities - Weighted Average Lives of Trading Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value
≥ 1 year and 3 years	$ 488,744	$ 389,883
≥ 3 years and 5 years	1,351,241	407,656
≥ 5 years	1,553,183	86,062
Securities, trading	3,393,168	883,601
Amortized Cost
≥ 1 year and 3 years	488,823	369,600
≥ 3 years and 5 years	1,339,604	375,030
Greater than or equal to five years	1,543,547	80,214
Amortized Cost	$ 3,371,974	$ 824,844