Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accounting Policies [Abstract]
Cash paid for interest		$ 23,722	$ 41,634
Cash paid for income taxes		28,043	44,140
Unsettled securities transactions		600,874	6,698
Loans foreclosed and transferred to other real estate owned and foreclosed assets		3,464	140
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities		4,045	18,284
Treasury stock issued to 401(k) stock purchase plan	$ 4,131	$ 1,749	$ 6,961