Loans Receivable and Allowance for Loan Losses (Summary of Loans Receivable by Credit Quality Risk Rating Indicator) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 6,121,844	$ 6,082,377
Loans and Leases Receivable, Gross	6,121,844	6,082,377
Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,245,711
Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,688,083
Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,070,294
Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	274,001
Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,278,089	4,208,488
Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,242,565	1,262,422
Loans and Leases Receivable, Gross	1,242,565	1,262,422
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans		611,467
Loans and Leases Receivable, Gross	601,190	611,467
Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	109,109	71,704
Special Mention [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	5,832	4,331
Special Mention [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	43,749	18,414
Special Mention [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,105	851
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	50,686	23,596
Special Mention [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	57,403	45,599
Special Mention [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,020	2,509
Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	84,455	110,364
Substandard [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	16,913	17,222
Substandard [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	30,773	53,454
Substandard [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	847	322
Substandard [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	347	2,600
Substandard [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	48,880	73,598
Substandard [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	32,410	32,828
Substandard [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	3,165	3,938
Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,089	1,092
Doubtful [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	0	0
Doubtful [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,061	1,063
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	1,061	1,063
Doubtful [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	28	29
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 [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 Loan [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
Total classified and criticized [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	194,653	183,160
Total classified and criticized [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	22,745	21,553
Total classified and criticized [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	75,583	72,931
Total classified and criticized [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,952	1,173
Total classified and criticized [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	347	2,600
Total classified and criticized [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	100,627	98,257
Total classified and criticized [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	89,841	78,456
Total classified and criticized [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	4,185	6,447
Pass/Watch [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	5,927,191	5,899,217
Pass/Watch [Member] | Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,222,966	1,229,892
Pass/Watch [Member] | Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,612,500	1,621,428
Pass/Watch [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	1,068,342	1,040,409
Pass/Watch [Member] | Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	273,654	218,502
Pass/Watch [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total mortgage loans	4,177,462	4,110,231
Pass/Watch [Member] | Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	1,152,724	1,183,966
Pass/Watch [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total loans	$ 597,005	$ 605,020