Business Combinations (Detail) $ in Thousands, shares in Millions			12 Months Ended
	Dec. 01, 2019 USD ($) office shares	Jan. 01, 2018 USD ($) branch shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) office
Business Acquisition [Line Items]
Loans			$ 29,537,449	$ 24,883,610
Core deposits
Business Acquisition [Line Items]
Estimated useful life			8 years 10 months 24 days
Oritani Financial Corp.
Business Acquisition [Line Items]
Assets	$ 4,292,319	$ 4,300,000
Loans	3,380,841	3,400,000
Deposits	$ 2,924,716	2,900,000
Number of branches acquired | office	26
Conversion ratio for shares issued	1.6
Consideration transferred	$ 835,300
Shares issued in connection with acquisition | shares	71.1
Merger expenses			$ 16,600
Oritani Financial Corp. | Core deposits
Business Acquisition [Line Items]
Estimated useful life			10 years
USAmeriBancorp, Inc.
Business Acquisition [Line Items]
Assets		5,100,000
Loans		3,700,000
Deposits		$ 3,600,000
Number of branches acquired | office				29
Conversion ratio for shares issued		6.1
Consideration transferred		$ 737,000
Shares issued in connection with acquisition | shares		64.9
Merger expenses				$ 17,400
USAmeriBancorp, Inc. | Alabama
Business Acquisition [Line Items]
Number of branches acquired | branch		15