Loans Receivable and Allowance for Credit Losses (Summary of Aging Loans Receivable by Portfolio Segment and Class) (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	$ 9,673,920	$ 9,593,879
Non-accrual	44,312	48,027
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	55,806	70,462
Non-accrual loans with no specific allowance	40,885	41,898
30 to 59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	9,732	15,827
60 to 89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	1,762	6,608
Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	9,618,114	9,523,417
Mortgage Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	7,226,005	7,077,571
Non-accrual	29,348	25,763
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	35,844	38,803
Non-accrual loans with no specific allowance	29,348	25,763
Mortgage Portfolio Segment | Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	1,194,613	1,202,638
Non-accrual	5,396	6,072
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	9,135	14,432
Non-accrual loans with no specific allowance	5,396	6,072
Mortgage Portfolio Segment | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	3,937,216	3,827,370
Non-accrual	19,533	16,887
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	19,815	21,567
Non-accrual loans with no specific allowance	19,533	16,887
Mortgage Portfolio Segment | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	1,394,761	1,364,397
Non-accrual	2,053	439
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	2,869	439
Non-accrual loans with no specific allowance	2,053	439
Mortgage Portfolio Segment | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	699,415	683,166
Non-accrual	2,366	2,365
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	4,025	2,365
Non-accrual loans with no specific allowance	2,366	2,365
Mortgage Portfolio Segment | 30 to 59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	5,142	7,949
Mortgage Portfolio Segment | 30 to 59 Days | Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	2,385	7,229
Mortgage Portfolio Segment | 30 to 59 Days | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	282	720
Mortgage Portfolio Segment | 30 to 59 Days | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	816	0
Mortgage Portfolio Segment | 30 to 59 Days | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	1,659	0
Mortgage Portfolio Segment | 60 to 89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	1,354	5,091
Mortgage Portfolio Segment | 60 to 89 Days | Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	1,354	1,131
Mortgage Portfolio Segment | 60 to 89 Days | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	0	3,960
Mortgage Portfolio Segment | 60 to 89 Days | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment | 60 to 89 Days | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment | Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	7,190,161	7,038,768
Mortgage Portfolio Segment | Current | Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	1,185,478	1,188,206
Mortgage Portfolio Segment | Current | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	3,917,401	3,805,803
Mortgage Portfolio Segment | Current | Multi-Family
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	1,391,892	1,363,958
Mortgage Portfolio Segment | Current | Construction
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	695,390	680,801
Commercial Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	2,131,326	2,188,866
Non-accrual	13,793	20,582
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	18,130	29,100
Non-accrual loans with no specific allowance	10,366	14,453
Commercial Loans | 30 to 59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	4,019	7,229
Commercial Loans | 60 to 89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	318	1,289
Commercial Loans | Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	2,113,196	2,159,766
Consumer Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	316,589	327,442
Non-accrual	1,171	1,682
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	1,832	2,559
Non-accrual loans with no specific allowance	1,171	1,682
Consumer Loans | 30 to 59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	571	649
Consumer Loans | 60 to 89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	90	228
Consumer Loans | Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total gross loans	$ 314,757	$ 324,883