Loans Receivable and Allowance for Loan Losses (Summary of Loans Receivable by Credit Quality Risk Rating Indicator) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	$ 7,226,980	$ 7,253,902
Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	183,965	162,966
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	83,146	87,801
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	100,617	74,242
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	202	923
Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	7,043,015	7,090,936
Mortgage Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	5,107,464	5,127,453
Mortgage Portfolio Segment [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	58,980	47,146
Mortgage Portfolio Segment [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	28,577	19,795
Mortgage Portfolio Segment [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	30,403	27,351
Mortgage Portfolio Segment [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	5,048,484	5,080,307
Mortgage Portfolio Segment [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,087,184	1,099,464
Mortgage Portfolio Segment [Member] | Residential [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	11,710	12,949
Mortgage Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	3,059	5,071
Mortgage Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	8,651	7,878
Mortgage Portfolio Segment [Member] | Residential [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Residential [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Residential [Member] | Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,075,474	1,086,515
Mortgage Portfolio Segment [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,288,342	2,299,313
Mortgage Portfolio Segment [Member] | Commercial [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	41,089	27,788
Mortgage Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	25,518	14,496
Mortgage Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	15,571	13,292
Mortgage Portfolio Segment [Member] | Commercial [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Commercial [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Commercial [Member] | Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,247,253	2,271,525
Mortgage Portfolio Segment [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,357,038	1,339,677
Mortgage Portfolio Segment [Member] | Multi-Family [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	228
Mortgage Portfolio Segment [Member] | Multi-Family [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	228
Mortgage Portfolio Segment [Member] | Multi-Family [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Multi-Family [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Multi-Family [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Multi-Family [Member] | Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,357,038	1,339,449
Mortgage Portfolio Segment [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	374,900	388,999
Mortgage Portfolio Segment [Member] | Construction [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	6,181	6,181
Mortgage Portfolio Segment [Member] | Construction [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Construction [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	6,181	6,181
Mortgage Portfolio Segment [Member] | Construction [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Construction [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Mortgage Portfolio Segment [Member] | Construction [Member] | Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	368,719	382,818
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,698,146	1,695,021
Commercial Loans [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	122,819	113,499
Commercial Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	54,481	67,396
Commercial Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	68,136	45,180
Commercial Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	202	923
Commercial Loans [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Commercial Loans [Member] | Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,575,327	1,581,522
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	421,370	431,428
Consumer Loans [Member] | Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,166	2,321
Consumer Loans [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	88	610
Consumer Loans [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,078	1,711
Consumer Loans [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer Loans [Member] | Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Consumer Loans [Member] | Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	$ 419,204	$ 429,107