Loans Receivable and Allowance for Loan Losses - Schedule of Summarized Loans Receivable (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 6,534,022	$ 6,082,377
Purchased Credit-Impaired Loans	3,435	4,510
Premiums on purchased loans	5,740	5,307
Unearned discounts	(41)	(53)
Net deferred fees	(5,482)	(6,636)
Loans receivable	6,537,674	6,085,505
Mortgage Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total mortgage loans	4,534,400	4,208,488
Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total mortgage loans	1,254,036	1,251,445
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total mortgage loans	1,714,923	1,694,359
Multi-Family [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total mortgage loans	1,233,792	1,041,582
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total mortgage loans	331,649	221,102
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	1,433,447	1,262,422
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 566,175	$ 611,467