Loans Receivable and Allowance for Loan Losses (Summary of Aging Loans Receivable by Portfolio Segment and Class) (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	$ 11,888	$ 13,665
60-89 Days	6,019	7,241
Non-accrual	46,075	53,855
Total Past Due and Non-accrual	63,982	74,761
Current	6,241,837	6,007,616
Total loans	6,305,819	6,082,377
Recorded Investment > 90 days accruing	0	0
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	1,012	1,000
60-89 Days	10	371
Non-accrual	11,805	12,342
Total Past Due and Non-accrual	12,827	13,713
Current	1,242,325	1,248,709
Total loans	1,255,152	1,262,422
Recorded Investment > 90 days accruing	0	0
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	2,702	2,398
60-89 Days	1,463	2,509
Non-accrual	4,022	3,944
Total Past Due and Non-accrual	8,187	8,851
Current	581,800	602,616
Total loans	589,987	611,467
Recorded Investment > 90 days accruing	0	0
Mortgage Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	8,174	10,267
60-89 Days	4,546	4,361
Non-accrual	30,248	37,569
Total Past Due and Non-accrual	42,968	52,197
Current	4,417,712	4,156,291
Total loans	4,460,680	4,208,488
Recorded Investment > 90 days accruing	0	0
Mortgage Loans [Member] | Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	7,610	10,121
60-89 Days	3,673	4,331
Non-accrual	11,961	17,222
Total Past Due and Non-accrual	23,244	31,674
Current	1,226,638	1,219,771
Total loans	1,249,882	1,251,445
Recorded Investment > 90 days accruing	0	0
Mortgage Loans [Member] | Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	564	146
60-89 Days	873	30
Non-accrual	17,440	20,026
Total Past Due and Non-accrual	18,877	20,202
Current	1,720,312	1,674,157
Total loans	1,739,189	1,694,359
Recorded Investment > 90 days accruing	0	0
Mortgage Loans [Member] | Multi-Family [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	0	0
60-89 Days	0	0
Non-accrual	847	321
Total Past Due and Non-accrual	847	321
Current	1,169,434	1,041,261
Total loans	1,170,281	1,041,582
Recorded Investment > 90 days accruing	0	0
Mortgage Loans [Member] | Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days	0	0
60-89 Days	0	0
Non-accrual	0	0
Total Past Due and Non-accrual	0	0
Current	301,328	221,102
Total loans	301,328	221,102
Recorded Investment > 90 days accruing	$ 0	$ 0