Balance Sheet Offsetting - Summary of Valley's Financial Instruments that are Eligible for Offset (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Offsetting Liabilities
Gross Amounts Recognized	$ 450,487	$ 367,218
Gross Amounts Offset	0	0
Net Amounts Presented	450,487	367,218
Gross Amounts Not Offset, Financial Instruments	(300,000)	(350,000)
Gross Amounts Not Offset, Cash Collateral	(150,487)	(16,881)
Net Amount	0	337
Repurchase agreements
Offsetting Liabilities
Gross Amounts Recognized	300,000	350,000
Gross Amounts Offset	0	0
Net Amounts Presented	300,000	350,000
Gross Amounts Not Offset, Financial Instruments	(300,000)	(350,000)
Gross Amounts Not Offset, Cash Collateral	0
Net Amount	0	0
Interest rate swaps
Offsetting Assets
Gross Amounts Recognized	150,487	17,218
Gross Amounts Offset	0	0
Net Amounts Presented	150,487	17,218
Gross Amounts Not Offset, Financial Instruments	0
Gross Amounts Not Offset, Cash Collateral	0	0
Net Amount	150,487	17,218
Offsetting Liabilities
Gross Amounts Recognized	150,487	17,218
Gross Amounts Offset	0	0
Net Amounts Presented	150,487	17,218
Gross Amounts Not Offset, Financial Instruments	0
Gross Amounts Not Offset, Cash Collateral	(150,487)	(16,881)
Net Amount	$ 0	$ 337