Fair Value Measurements - Valuation of Financial Instruments That are Marked-to-Market on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Assets:
Trading investments	$ 52,450	$ 37,465
Available-for-sale investments	2,427,540	2,517,956
Derivative instruments	1,121	1,317
Liabilities:
Derivative instruments	0	(247)
Fair Value Measurements on a Recurring Basis
Assets:
Trading investments	52,450	37,465
Available-for-sale investments	2,427,540	2,517,956
Derivative instruments	2,172	1,322
Total earning assets	2,482,162	2,556,743
Liabilities:
Derivative instruments	(1,051)	(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	2,427,540	2,517,956
Derivative instruments	2,172	1,322
Total earning assets	2,429,712	2,519,278
Liabilities:
Derivative instruments	(1,051)	(252)
Fair Value Measurements on a Recurring Basis | Level 3
Assets:
Trading investments	52,450	37,465
Available-for-sale investments	0	0
Derivative instruments	0	0
Total earning assets	52,450	37,465
Liabilities:
Derivative instruments	$ 0	$ 0