Loans Receivable and Allowance for Loan Losses (Summary of Loans Receivable by Credit Quality Risk Rating Indicator) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	$ 4,798,893	$ 4,534,400
Total gross loans	6,890,560	6,534,022
Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,213,507	1,254,036
Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,884,155	1,714,923
Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,384,428	1,233,792
Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	316,803	331,649
Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,798,893	4,534,400
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,553,606	1,433,447
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	538,061	566,175
Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	127,229	191,332
Total classified and criticized [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	20,128	17,465
Total classified and criticized [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	46,641	48,814
Total classified and criticized [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,237	2,328
Total classified and criticized [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	2,517	2,351
Total classified and criticized [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	70,523	70,958
Total classified and criticized [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	52,978	115,126
Total classified and criticized [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	3,728	5,248
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	48,209	113,535
Special Mention [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	7,579	5,434
Special Mention [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	21,595	29,363
Special Mention [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	1,080
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	29,174	35,877
Special Mention [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	18,035	76,464
Special Mention [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,000	1,194
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	79,020	77,789
Substandard [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	12,549	12,031
Substandard [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	25,046	19,451
Substandard [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,237	1,248
Substandard [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	2,517	2,351
Substandard [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	41,349	35,081
Substandard [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	34,943	38,654
Substandard [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	2,728	4,054
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	0	8
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	8
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	6,763,331	6,342,690
Pass/Watch [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,193,379	1,236,571
Pass/Watch [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,837,514	1,666,109
Pass/Watch [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,383,191	1,231,464
Pass/Watch [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	314,286	329,298
Pass/Watch [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,728,370	4,463,442
Pass/Watch [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	1,500,628	1,318,321
Pass/Watch [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total gross loans	$ 534,333	$ 560,927