Summary of Significant Accounting Policies (Additional Cash Flow Information) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash paid for interest	$ 49,300	$ 124,781	$ 89,270
Cash paid for income tax	44,140	45,352	5,112
Transfer of securities from available for sale to held to maturity	0	377,812	0
Unsettled securities transactions	57,783	0	330
Loans foreclosed and transferred to other real estate owned and foreclosed assets	140	1,348	2,899
Loans to facilitate the sale of other real estate owned	0	847	0
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities	18,284	319,286	0
Treasury stock issued to 401(k) stock purchase plan	$ 10,307	$ 0	$ 0