Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Accounting Policies [Abstract]
Cash paid for interest		$ 41,634	$ 100,041
Cash paid for income taxes		44,140	42,352
Unsettled securities transactions		6,698	82,064
Loans foreclosed and transferred to other real estate owned and foreclosed assets		140	1,302
Loans to facilitate the sale of other real estate owned		0	847
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities		18,284	315,542
Treasury stock issued to 401(k) stock purchase plan	$ 4,131	$ 6,961	$ 0