Fair Value Measurements - Valuation of Financial Instruments that are Marked-to-Market on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets:
Trading investments	$ 37,465	$ 16,923
Available-for-sale investments	2,517,956	1,996,634
Fair Value Measurements Recurring
Assets:
Trading investments	37,465	16,923
Available-for-sale investments	2,517,956	1,996,634
Derivative instruments	1,322	729
Total	2,556,743	2,014,286
Liabilities:
Derivative instruments	(252)	(287)
Fair Value Measurements Recurring \| Level 1
Assets:
Trading investments	0	0
Available-for-sale investments	0	0
Derivative instruments	0	0
Total	0	0
Liabilities:
Derivative instruments	0	0
Fair Value Measurements Recurring \| Level 2
Assets:
Trading investments	0	0
Available-for-sale investments	2,517,956	1,996,634
Derivative instruments	1,322	729
Total	2,519,278	1,997,363
Liabilities:
Derivative instruments	(252)	(287)
Fair Value Measurements Recurring \| Level 3
Assets:
Trading investments	37,465	16,923
Available-for-sale investments	0	0
Derivative instruments	0	0
Total	37,465	16,923
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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