Fair Value Measurements - Valuation of Financial Instruments that are Marked-to-Market on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Assets:
Trading investments	$ 55,903	$ 37,465
Available-for-sale investments	2,342,089	2,517,956
Derivative instruments	$ 405	$ 1,317
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Liabilities:
Derivative instruments	$ 0	$ (247)
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other liabilities	Other liabilities
Fair Value Measurements Recurring
Assets:
Trading investments	$ 55,903	$ 37,465
Available-for-sale investments	2,342,089	2,517,956
Derivative instruments	972	1,322
Total	2,398,964	2,556,743
Liabilities:
Derivative instruments	(567)	(252)
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	2,342,089	2,517,956
Derivative instruments	972	1,322
Total	2,343,061	2,519,278
Liabilities:
Derivative instruments	(567)	(252)
Fair Value Measurements Recurring | Level 3
Assets:
Trading investments	55,903	37,465
Available-for-sale investments	0	0
Derivative instruments	0	0
Total	55,903	37,465
Liabilities:
Derivative instruments	$ 0	$ 0