Fair Value Measurements - Valuation of Financial Instruments That are Marked-to-Market on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets
Trading investments	$ 38,820	$ 37,465
Available-for-sale investments	2,341,551	2,517,956
Fair Value Measurements on a Recurring Basis
Assets
Trading investments	38,820	37,465
Available-for-sale investments	2,341,551	2,517,956
Derivative instruments	169	1,322
Total earning assets	2,380,540	2,556,743
Liabilities
Derivative instruments	(263)	(252)
Fair Value Measurements on a Recurring Basis \| Level 1
Assets
Trading investments	0	0
Available-for-sale investments	0	0
Derivative instruments	0	0
Total earning assets	0	0
Liabilities
Derivative instruments	0	0
Fair Value Measurements on a Recurring Basis \| Level 2
Assets
Trading investments	0	0
Available-for-sale investments	2,341,551	2,517,956
Derivative instruments	169	1,322
Total earning assets	2,341,720	2,519,278
Liabilities
Derivative instruments	(263)	(252)
Fair Value Measurements on a Recurring Basis \| Level 3
Assets
Trading investments	38,820	37,465
Available-for-sale investments	0	0
Derivative instruments	0	0
Total earning assets	38,820	37,465
Liabilities
Derivative instruments	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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