Fair Value Measurements - Valuation of Financial Instruments that are Marked-to-Market on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets:
Trading investments	$ 54,481	$ 55,903
Available-for-sale investments	2,411,622	2,342,089
Derivative instruments	$ 0	$ 405
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Liabilities:
Derivative instruments	$ (370)	$ 0
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other liabilities	Other liabilities
Level 3
Assets:
Trading investments	$ 54,000	$ 56,000
Fair Value Measurements Recurring
Assets:
Trading investments	54,481	55,903
Available-for-sale investments	2,411,622	2,342,089
Derivative instruments	0	972
Total	2,466,103	2,398,964
Liabilities:
Derivative instruments	(370)	(567)
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	2,411,622	2,342,089
Derivative instruments	0	972
Total	2,411,622	2,343,061
Liabilities:
Derivative instruments	(370)	(567)
Fair Value Measurements Recurring | Level 3
Assets:
Trading investments	54,481	55,903
Available-for-sale investments	0	0
Derivative instruments	0	0
Total	54,481	55,903
Liabilities:
Derivative instruments	$ 0	$ 0