Loans Receivable and Allowance for Loan Losses (Schedule of Allowance for Loan Losses by Portfolio Segment) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 62,191	$ 61,110	$ 61,424	$ 61,734
Provision charged to operations	1,700	1,100	3,200	1,700
Recoveries of loans previously charged-off	813	987	1,393	1,478
Loans charged-off	(3,771)	(3,573)	(5,084)	(5,288)
Balance at end of period	60,933	59,624	60,933	59,624
Mortgage Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	30,849	32,886	32,094	31,977
Provision charged to operations	497	317	(695)	1,355
Recoveries of loans previously charged-off	401	71	573	136
Loans charged-off	(113)	(1,450)	(338)	(1,644)
Balance at end of period	31,634	31,824	31,634	31,824
Commercial Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	28,255	23,697	25,829	24,381
Provision charged to operations	1,311	(202)	4,269	(678)
Recoveries of loans previously charged-off	192	660	283	874
Loans charged-off	(3,459)	(1,315)	(4,082)	(1,737)
Balance at end of period	26,299	22,840	26,299	22,840
Consumer Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	3,087	4,277	3,501	4,881
Provision charged to operations	(108)	845	(374)	1,129
Recoveries of loans previously charged-off	220	256	537	467
Loans charged-off	(199)	(808)	(664)	(1,907)
Balance at end of period	3,000	4,570	3,000	4,570
Total Portfolio Segments [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	62,191	60,860	61,424	61,239
Provision charged to operations	1,700	960	3,200	1,806
Recoveries of loans previously charged-off	813	987	1,393	1,477
Loans charged-off	(3,771)	(3,573)	(5,084)	(5,288)
Balance at end of period	60,933	59,234	60,933	59,234
Unallocated [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	0	250	0	495
Provision charged to operations	0	140	0	(106)
Recoveries of loans previously charged-off	0	0	0	1
Loans charged-off	0	0	0	0
Balance at end of period	$ 0	$ 390	$ 0	$ 390