Benefit Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Apr. 19, 2021
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Discount rate used to compute the obligation	2.52%	3.32%
Employer contributions	$ 1,353	$ 1,351
Projected benefit obligation	190,849	175,405
Obligation included in other comprehensive loss, net of tax	36,461	33,437
Benefit expense	(11,256)	(10,076)	$ (9,745)
Salary expense	25,100	19,100	18,800
Expense for contributions to savings and investment plan	$ 10,100	8,600	8,500
Maximum annual salary deferral, percent	5.00%
Vesting period of employer matching contributions	2 years
Unsecured general liability	$ 1,700	1,000
Shares of common stock available for issuance (in shares)	3,000,000.0
Stock-based compensation expense	$ 16,154	14,726	19,472
Unrecognized stock-based compensation	$ 17,800
Average remaining vesting, years	1 year 9 months 3 days
Award vesting period	1 year
Vesting percentage	8.33%
Stock Options and Restricted Stock
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Stock-based compensation expense	$ 16,500	15,000	19,500
Stock awards granted	$ 1,500	$ 2,100	$ 4,300
Share-based compensation, expiration period	1 year	1 year
RSUs
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Award vesting period	3 years
Vesting percentage	33.33%
Granted (in shares)	2,030,026	1,412,941	509,725
Performance Shares
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Award vesting period	3 years
Restricted Stock
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Granted (in shares)	0	0	1,263,144
Subsequent event | Forecast
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Share-based compensation, shares authorized (in shares)				9,000,000
Employee Stock Incentive Plan | Performance-Based RSU
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Weighted average grant date fair value (usd per share)	$ 10.82	$ 10.43	$ 12.36
Employee Stock Incentive Plan | Time-Based RSU
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Weighted average grant date fair value (usd per share)	$ 10.29	$ 10.32
Non-Employee Directors | Restricted Stock
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Granted (in shares)			60,000
Qualified Plan | Other pension plan
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Employer contributions	$ 1,100
Nonqualified Plan
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Projected benefit obligation	20,513	$ 20,081
Expense for contributions to savings and investment plan	372	273	$ 262
Nonqualified Plan | Oritani Financial Corp.
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Split dollar life insurance liability	1,800	961
Nonqualified Plan | Oritani Financial Corp. | Split-Dollar Plan
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Benefit expense	812
Nonqualified Plan | Former Directors And Senior Management
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Projected benefit obligation	399	451
Obligation included in other comprehensive loss, net of tax	731	803
Obligation included in other comprehensive loss, tax	286	314
Obligation included in other comprehensive loss, net of tax, amount expected to be reclassified	1,000
Nonqualified Plan | Other pension plan | Oritani Financial Corp.
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Projected benefit obligation	1,300	1,600
Nonqualified Plan | Other pension plan | Non Qualified Plans For Former Directors
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Projected benefit obligation	1,400	1,600
Nonqualified Plan | Benefit equalization plans | Oritani Financial Corp.
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Projected benefit obligation		26,800
Nonqualified Plan | Supplemental Executive Retirement Income Agreement | Oritani Financial Corp.
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Projected benefit obligation	$ 13,600	$ 13,000
Benefits payment period	20 years
Benefit expense	$ 1,500
Fixed income securities | Qualified Plan
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Target asset allocation percentage	50.00%
Fixed income securities | Qualified Plan | Consumer Price Index
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Cumulative annual real return, period	5 years
Fixed income securities | Qualified Plan | Merrill Lynch Intermediate Government/Corporate Index
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Cumulative annual real return, period	3 years
Equity securities | Qualified Plan
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Target asset allocation percentage	50.00%
Equity securities | Qualified Plan | Consumer Price Index
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Cumulative annual real return, period	5 years
Equity securities | Qualified Plan | S&P 500 Index
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Cumulative annual real return, period	3 years