Loans Receivable and Allowance for Loan Losses - Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period				$ 61,734				$ 64,664	$ 61,734	$ 64,664	$ 70,348
Provision charged to operations	$ 1,250	$ 1,400	$ 1,100	600	$ 1,250	$ 1,500	$ 1,500	400	4,350	4,650	5,500
Recoveries of loans previously charged off									4,168	3,292	3,222
Loans charged off									(8,828)	(10,872)	(14,406)
Balance at end of period	61,424				61,734				61,424	61,734	64,664
Mortgage Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period				31,977				34,144	31,977	34,144
Provision charged to operations									2,357	1,455
Recoveries of loans previously charged off									247	286
Loans charged off									(2,487)	(3,908)
Balance at end of period	32,094				31,977				32,094	31,977	34,144
Commercial Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period				24,381				24,107	24,381	24,107
Provision charged to operations									1,898	2,947
Recoveries of loans previously charged off									2,413	1,776
Loans charged off									(2,863)	(4,449)
Balance at end of period	25,829				24,381				25,829	24,381	24,107
Consumer Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period				4,881				4,929	4,881	4,929
Provision charged to operations									590	1,237
Recoveries of loans previously charged off									1,508	1,230
Loans charged off									(3,478)	(2,515)
Balance at end of period	3,501				4,881				3,501	4,881	4,929
Total Portfolio Segments [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period				61,239				63,180	61,239	63,180
Provision charged to operations									4,845	5,639
Recoveries of loans previously charged off									4,168	3,292
Loans charged off									(8,828)	(10,872)
Balance at end of period	61,424				61,239				61,424	61,239	63,180
Unallocated [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period				$ 495				$ 1,484	495	1,484
Provision charged to operations									(495)	(989)
Recoveries of loans previously charged off									0	0
Loans charged off									0	0
Balance at end of period	$ 0				$ 495				$ 0	$ 495	$ 1,484