Loans Receivable and Allowance for Loan Losses - Summary of Aging Loans Receivable by Portfolio Segment and Class (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	$ 44,371	$ 53,855
90 days or more past due and accruing	165	0
Total Past Due	68,727	74,761
Current	6,465,295	6,007,616
Total Loans Receivable	6,534,022	6,082,377
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	23,875	12,342
90 days or more past due and accruing	165	0
Total Past Due	25,473	13,713
Current	1,407,974	1,248,709
Total Loans Receivable	1,433,447	1,262,422
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	4,109	3,944
90 days or more past due and accruing	0	0
Total Past Due	8,906	8,851
Current	557,269	602,616
Total Loans Receivable	566,175	611,467
Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	16,387	37,569
90 days or more past due and accruing	0	0
Total Past Due	34,348	52,197
Current	4,500,052	4,156,291
Total Loans Receivable	4,534,400	4,208,488
Mortgage Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	12,031	17,222
90 days or more past due and accruing	0	0
Total Past Due	26,448	31,674
Current	1,227,588	1,219,771
Total Loans Receivable	1,254,036	1,251,445
Mortgage Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	1,263	20,026
90 days or more past due and accruing	0	0
Total Past Due	3,538	20,202
Current	1,711,385	1,674,157
Total Loans Receivable	1,714,923	1,694,359
Mortgage Loans [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	742	321
90 days or more past due and accruing	0	0
Total Past Due	2,011	321
Current	1,231,781	1,041,261
Total Loans Receivable	1,233,792	1,041,582
Mortgage Loans [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Non-accrual	2,351	0
90 days or more past due and accruing	0	0
Total Past Due	2,351	0
Current	329,298	221,102
Total Loans Receivable	331,649	221,102
Financing Receivables, 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	15,713	13,665
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	632	1,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	3,603	2,398
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	11,478	10,267
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	8,983	10,121
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	1,732	146
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	763	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Mortgage Loans [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	8,478	7,241
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	801	371
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	1,194	2,509
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	6,483	4,361
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	5,434	4,331
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	543	30
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	506	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Mortgage Loans [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans receivable past due	$ 0	$ 0