Loans Receivable and Allowance for Loan Losses (Summary of Aging Loans Receivable by Portfolio Segment and Class) (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 50,649	$ 44,371
Recorded Investment greater than 90 days accruing	0	165
Total Past Due	73,717	68,727
Current	6,561,446	6,465,295
Total loans	6,635,163	6,534,022
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	28,527	23,875
Recorded Investment greater than 90 days accruing	0	165
Total Past Due	29,635	25,473
Current	1,449,510	1,407,974
Total loans	1,479,145	1,433,447
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,996	4,109
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	6,199	8,906
Current	549,857	557,269
Total loans	556,056	566,175
Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	19,126	16,387
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	37,883	34,348
Current	4,562,079	4,500,052
Total loans	4,599,962	4,534,400
Mortgage Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	14,063	12,031
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	27,556	26,448
Current	1,235,553	1,227,588
Total loans	1,263,109	1,254,036
Mortgage Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	1,306	1,263
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	5,772	3,538
Current	1,703,282	1,711,385
Total loans	1,709,054	1,714,923
Mortgage Loans [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	1,240	742
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	2,038	2,011
Current	1,316,105	1,231,781
Total loans	1,318,143	1,233,792
Mortgage Loans [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,517	2,351
Recorded Investment greater than 90 days accruing	0	0
Total Past Due	2,517	2,351
Current	307,139	329,298
Total loans	309,656	331,649
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Recorded investment past due	14,034	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	1,108	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	2,762	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	10,164	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	9,002	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	1,115	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	47	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	9,034	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	0	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	441	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	8,593	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	4,491	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	3,351	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	751	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