Loans Receivable and Allowance for Loan Losses (Summary of Loans Receivable by Credit Quality Risk Rating Indicator) (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	$ 4,836,463	$ 4,857,109
Total gross loans	6,999,116	7,004,308
Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,198,009	1,211,672
Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,966,075	1,978,569
Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,399,013	1,402,054
Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	273,366	264,814
Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,836,463	4,857,109
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,660,290	1,630,444
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	502,363	516,755
Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	142,816	136,834
Total classified and criticized [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	14,335	18,584
Total classified and criticized [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	49,768	48,340
Total classified and criticized [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,161	1,116
Total classified and criticized [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	2,517	2,517
Total classified and criticized [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	67,781	70,557
Total classified and criticized [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	71,150	62,095
Total classified and criticized [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	3,885	4,182
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	60,890	48,537
Special Mention [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,310	6,563
Special Mention [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	24,492	25,329
Special Mention [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	557	563
Special Mention [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Special Mention [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	29,359	32,455
Special Mention [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	30,538	14,840
Special Mention [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	993	1,242
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	81,926	88,297
Substandard [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	10,025	12,021
Substandard [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	25,276	23,011
Substandard [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	604	553
Substandard [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	2,517	2,517
Substandard [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	38,422	38,102
Substandard [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	40,612	47,255
Substandard [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,892	2,940
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Doubtful [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Doubtful [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Doubtful [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Doubtful [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Doubtful [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Doubtful [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Doubtful [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Loss [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Loss [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Loss [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Loss [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Loss [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Loss [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Loss [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	0
Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	6,856,300	6,867,474
Pass/Watch [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,183,674	1,193,088
Pass/Watch [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,916,307	1,930,229
Pass/Watch [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,397,852	1,400,938
Pass/Watch [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	270,849	262,297
Pass/Watch [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,768,682	4,786,552
Pass/Watch [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,589,140	1,568,349
Pass/Watch [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	$ 498,478	$ 512,573