Investments - Gross Unrealized Gains and Losses and Cost of Equity (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Equity securities, Cost	$ 36,019	$ 44,046
Equity securities, Gross Unrealized Gains	17,851	13,101
Equity securities, Gross Unrealized Losses	(31)
Equity securities	53,839	57,147
Domestic Common Stock [Member]
Schedule Of Trading Securities And Other Trading Assets [Line Items]
Equity securities, Cost	36,019	44,046
Equity securities, Gross Unrealized Gains	17,851	13,101
Equity securities, Gross Unrealized Losses	(31)
Equity securities	$ 53,839	$ 57,147