Loans Receivable and Allowance for Loan Losses (Summary of Aging Loans Receivable by Portfolio Segment and Class) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 40,016	$ 44,371
Recorded Investment greater than 90 days accruing	0	165
Total Past Due	61,755	68,727
Current	6,828,805	6,465,295
Total gross loans	6,890,560	6,534,022
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	16,436	23,875
Recorded Investment greater than 90 days accruing	0	165
Total Past Due	18,487	25,473
Current	1,535,119	1,407,974
Total gross loans	1,553,606	1,433,447
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,779	4,109
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	6,167	8,906
Current	531,894	557,269
Total gross loans	538,061	566,175
Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	20,801	16,387
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	37,101	34,348
Current	4,761,792	4,500,052
Total gross loans	4,798,893	4,534,400
Mortgage Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	11,317	12,031
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	26,043	26,448
Current	1,187,464	1,227,588
Total gross loans	1,213,507	1,254,036
Mortgage Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	5,679	1,263
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	7,253	3,538
Current	1,876,902	1,711,385
Total gross loans	1,884,155	1,714,923
Mortgage Loans [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	1,113	742
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	1,113	2,011
Current	1,383,315	1,231,781
Total gross loans	1,384,428	1,233,792
Mortgage Loans [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,692	2,351
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	2,692	2,351
Current	314,111	329,298
Total gross loans	316,803	331,649
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	12,863	15,713
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	1,754	632
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	2,388	3,603
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	8,721	11,478
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	7,147	8,983
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	1,574	1,732
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	763
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	8,876	8,478
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	297	801
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	1,000	1,194
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	7,579	6,483
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	7,579	5,434
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	0	543
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	506
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