Loans Receivable and Allowance for Loan Losses (Summary of Loans Receivable by Credit Quality Risk Rating Indicator) (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	$ 4,599,962	$ 4,534,400
Total loans	6,635,163	6,534,022
Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,263,109	1,254,036
Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,709,054	1,714,923
Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,318,143	1,233,792
Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	309,656	331,649
Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,599,962	4,534,400
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,479,145	1,433,447
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	556,056	566,175
Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	163,609	191,332
Total classified and criticized [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	18,554	17,465
Total classified and criticized [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	40,226	48,814
Total classified and criticized [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,991	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	63,288	70,958
Total classified and criticized [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	96,938	115,126
Total classified and criticized [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,383	5,248
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	89,437	113,535
Special Mention [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,491	5,434
Special Mention [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	27,574	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	32,065	35,877
Special Mention [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	56,931	76,464
Special Mention [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	441	1,194
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	70,170	77,789
Substandard [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	14,063	12,031
Substandard [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	12,652	19,451
Substandard [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,991	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	31,223	35,081
Substandard [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	36,005	38,654
Substandard [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	2,942	4,054
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,002	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 loans	4,002	8
Doubtful [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Loss [Member]
Financing Receivable, Recorded Investment [Line Items]
Total 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 loans	0	0
Loss [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	0	0
Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	6,471,554	6,342,690
Pass/Watch [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,244,555	1,236,571
Pass/Watch [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,668,828	1,666,109
Pass/Watch [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,316,152	1,231,464
Pass/Watch [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	307,139	329,298
Pass/Watch [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,536,674	4,463,442
Pass/Watch [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,382,207	1,318,321
Pass/Watch [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 552,673	$ 560,927