Loans Receivable and Allowance for Credit Losses (Summary of Loans Receivable by Credit Quality Risk Rating Indicator) (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 7,766,391	$ 7,332,885
Total gross loans	7,780,267
2020	952,336
2019	1,269,766
2018	996,015
2017	909,531
2016 and prior	3,939,662
Total classified and criticized
Financing Receivable, Recorded Investment [Line Items]
Total loans	402,136	218,056
2020	4,727
2019	28,897
2018	25,248
2017	56,222
2016 and prior	287,042
Criticized and classified loans, gross	404,100
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	257,683	128,694
2020	4,562
2019	25,418
2018	19,853
2017	34,334
2016 and prior	173,516
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	144,353	88,526
2020	165
2019	3,479
2018	5,395
2017	21,888
2016 and prior	113,426
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	100	836
2020	0
2019	0
2018	0
2017	0
2016 and prior	100
Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	7,378,131	7,119,508
2020	947,609
2019	1,240,869
2018	970,767
2017	853,309
2016 and prior	3,652,620
Residential | Special Mention | Payment Deferral
Financing Receivable, Recorded Investment [Line Items]
Total loans	45,600
Residential | Substandard | Payment Deferral
Financing Receivable, Recorded Investment [Line Items]
Total loans	10,400
Mortgage Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	5,362,401	5,311,445
2020	426,830
2019	982,197
2018	761,582
2017	671,224
2016 and prior	2,605,919
Mortgage Portfolio Segment | Total classified and criticized
Financing Receivable, Recorded Investment [Line Items]
Total loans	145,514	79,003
2020	4,639
2019	21,375
2018	12,569
2017	21,581
2016 and prior	85,350
Mortgage Portfolio Segment | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	100,450	49,160
2020	4,474
2019	18,201
2018	9,720
2017	6,833
2016 and prior	61,222
Mortgage Portfolio Segment | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	45,064	29,843
2020	165
2019	3,174
2018	2,849
2017	14,748
2016 and prior	24,128
Mortgage Portfolio Segment | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,216,887	5,232,442
2020	422,191
2019	960,822
2018	749,013
2017	649,643
2016 and prior	2,520,569
Mortgage Portfolio Segment | Residential
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,125,407
2020	139,828
2019	152,496
2018	91,836
2017	88,026
2016 and prior	697,209
Mortgage Portfolio Segment | Residential | Total classified and criticized
Financing Receivable, Recorded Investment [Line Items]
Total loans	69,726	12,606
2020	3,767
2019	8,941
2018	8,979
2017	4,051
2016 and prior	43,988
Mortgage Portfolio Segment | Residential | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	50,250	2,402
2020	3,602
2019	5,767
2018	6,130
2017	3,321
2016 and prior	31,430
Mortgage Portfolio Segment | Residential | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	19,476	10,204
2020	165
2019	3,174
2018	2,849
2017	730
2016 and prior	12,558
Mortgage Portfolio Segment | Residential | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Residential | Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Residential | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,055,681	1,065,083
2020	136,061
2019	143,555
2018	82,857
2017	83,975
2016 and prior	653,221
Mortgage Portfolio Segment | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,676,426
2020	226,407
2019	559,046
2018	369,249
2017	408,198
2016 and prior	1,154,663
Mortgage Portfolio Segment | Commercial | Total classified and criticized
Financing Receivable, Recorded Investment [Line Items]
Total loans	74,691	60,216
2020	0
2019	12,434
2018	3,590
2017	17,530
2016 and prior	41,137
Mortgage Portfolio Segment | Commercial | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	49,227	46,758
2020	0
2019	12,434
2018	3,590
2017	3,512
2016 and prior	29,691
Mortgage Portfolio Segment | Commercial | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	25,464	13,458
2020	0
2019	0
2018	0
2017	14,018
2016 and prior	11,446
Mortgage Portfolio Segment | Commercial | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Commercial | Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Commercial | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,601,735	2,518,177
2020	226,407
2019	546,612
2018	365,659
2017	390,668
2016 and prior	1,113,526
Mortgage Portfolio Segment | Multi-Family
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,275,588
2020	55,630
2019	139,753
2018	190,357
2017	136,026
2016 and prior	754,047
Mortgage Portfolio Segment | Multi-Family | Total classified and criticized
Financing Receivable, Recorded Investment [Line Items]
Total loans	225	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	225
Mortgage Portfolio Segment | Multi-Family | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	101	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	101
Mortgage Portfolio Segment | Multi-Family | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	124	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	124
Mortgage Portfolio Segment | Multi-Family | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Multi-Family | Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Multi-Family | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,275,363	1,225,551
2020	55,630
2019	139,753
2018	190,357
2017	136,026
2016 and prior	753,822
Mortgage Portfolio Segment | Construction
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	284,980
2020	4,965
2019	130,902
2018	110,140
2017	38,974
2016 and prior	0
Mortgage Portfolio Segment | Construction | Total classified and criticized
Financing Receivable, Recorded Investment [Line Items]
Total loans	872	6,181
2020	872
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Construction | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	872	0
2020	872
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	6,181
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Construction | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Construction | Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Mortgage Portfolio Segment | Construction | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	284,108	423,631
2020	4,093
2019	130,902
2018	110,140
2017	38,974
2016 and prior	0
Commercial Loans
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,056,213	1,634,759
2020	509,664
2019	236,093
2018	189,318
2017	202,675
2016 and prior	1,116,188
Commercial Loans | Total classified and criticized
Financing Receivable, Recorded Investment [Line Items]
Total loans	251,691	137,099
2020	63
2019	7,179
2018	12,083
2017	34,641
2016 and prior	197,725
Commercial Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	155,365	79,248
2020	63
2019	6,922
2018	9,841
2017	27,501
2016 and prior	111,038
Commercial Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	96,226	57,015
2020	0
2019	257
2018	2,242
2017	7,140
2016 and prior	86,587
Commercial Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	100	836
2020	0
2019	0
2018	0
2017	0
2016 and prior	100
Commercial Loans | Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Commercial Loans | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,804,522	1,497,660
2020	509,601
2019	228,914
2018	177,235
2017	168,034
2016 and prior	918,463
Consumer Loans
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	361,653
2020	15,842
2019	51,476
2018	45,115
2017	35,632
2016 and prior	217,555
Consumer Loans | Total classified and criticized
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,931	1,954
2020	25
2019	343
2018	596
2017	0
2016 and prior	3,967
Consumer Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,868	286
2020	25
2019	295
2018	292
2017	0
2016 and prior	1,256
Consumer Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,063	1,668
2020	0
2019	48
2018	304
2017	0
2016 and prior	2,711
Consumer Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Consumer Loans | Loss
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
2020	0
2019	0
2018	0
2017	0
2016 and prior	0
Consumer Loans | Pass/Watch
Financing Receivable, Recorded Investment [Line Items]
Total loans	356,722	$ 389,406
2020	15,817
2019	51,133
2018	44,519
2017	35,632
2016 and prior	$ 213,588