Balance Sheet Offsetting - Summary of Valley's Financial Instruments that are Eligible for Offset (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Offsetting Liabilities
Gross Amounts Recognized	$ 172,907	$ 224,212
Gross Amounts Offset	0	0
Net Amounts Presented	172,907	224,212
Gross Amounts Not Offset, Financial Instruments	(1,214)	(5,376)
Gross Amounts Not Offset, Cash Collateral	(151,852)	(208,141)
Net Amount	19,841	10,695
Repurchase agreements
Offsetting Liabilities
Gross Amounts Recognized	150,000	200,000
Gross Amounts Offset	0	0
Total long-term securities sold under agreements to repurchase	150,000	200,000
Gross Amounts Not Offset, Financial Instruments	0	0
Gross Amounts Not Offset, Cash Collateral	(150,000)	(200,000)
Net Amount	0	0
Interest rate caps and swaps
Offsetting Assets
Gross Amounts Recognized	48,642	26,346
Gross Amounts Offset	0	0
Net Amounts Presented	48,642	26,346
Gross Amounts Not Offset, Financial Instruments	(1,214)	(5,376)
Gross Amounts Not Offset, Cash Collateral	0	0
Net Amount	47,428	20,970
Offsetting Liabilities
Gross Amounts Recognized	22,907	24,212
Gross Amounts Offset	0	0
Net Amounts Presented	22,907	24,212
Gross Amounts Not Offset, Financial Instruments	(1,214)	(5,376)
Gross Amounts Not Offset, Cash Collateral	(1,852)	(8,141)
Net Amount	$ 19,841	$ 10,695