Loans Receivable and Allowance for Loan Losses (Summary of Aging Loans Receivable by Portfolio Segment and Class) (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 40,493	$ 42,401
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	60,759	60,708
Current	6,938,357	6,943,600
Total gross loans	6,999,116	7,004,308
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	17,572	16,787
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	19,091	18,800
Current	1,641,199	1,611,644
Total gross loans	1,660,290	1,630,444
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,892	3,030
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	6,937	6,790
Current	495,426	509,965
Total gross loans	502,363	516,755
Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	20,029	22,584
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	34,731	35,118
Current	4,801,732	4,821,991
Total gross loans	4,836,463	4,857,109
Mortgage Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	10,025	12,021
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	21,510	24,475
Current	1,176,499	1,187,197
Total gross loans	1,198,009	1,211,672
Mortgage Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	7,408	7,493
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	10,625	7,573
Current	1,955,450	1,970,996
Total gross loans	1,966,075	1,978,569
Mortgage Loans [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	79	553
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	79	553
Current	1,398,934	1,401,501
Total gross loans	1,399,013	1,402,054
Mortgage Loans [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,517	2,517
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	2,517	2,517
Current	270,849	262,297
Total gross loans	273,366	264,814
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	13,208	10,108
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	709	1,656
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	3,052	2,561
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	9,447	5,891
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	7,175	5,891
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	2,272	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	7,058	8,199
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	810	357
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	993	1,199
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	5,255	6,643
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	4,310	6,563
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	945	80
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	$ 0	$ 0