Tax Effects of Temporary Differences that Give Rise to Significant Portions of Deferred Tax Assets and Deferred Tax Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Loss and LAE reserves	$ 144,500	$ 132,300
Foreign tax credit carry forward	59,200	74,100
Compensation accruals	99,700	87,500
Unearned premiums	114,100	112,200
Allowance for credit losses on available for sale securities	5,200	5,700
State net operating loss carry forward	13,200	12,500
Other	97,800	98,000
Gross deferred tax assets before valuation allowance	533,700	522,300
Valuation allowance	(12,900)	(12,500)
Gross deferred tax assets	520,800	509,800
Deferred tax liabilities:
Net unrealized gains on investments	308,400	294,700
Deferred acquisition costs	127,000	128,400
Purchase accounting adjustments	11,200	11,700
Other	131,200	118,500
Gross deferred tax liabilities	577,800	553,300
Net deferred tax (liabilities)	$ (56,958)	$ (43,547)