Significant Accounting Policies - Additional Cash Flow Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accounting Policies [Abstract]
Cash paid for interest		$ 15,936	$ 31,712
Cash paid for income taxes		15,400	32,174
Unsettled securities transactions		358,752	216,855
Loans foreclosed and transferred to other real estate owned and foreclosed assets		3,251	0
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities		1,552	18,679
Treasury stock issued to 401(k) stock purchase plan	$ 2,830	$ 1,749	$ 2,830