Investment Securities (Disclosure Regarding Length of Time on Securities Available for Sale with Temporary Impairment) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	$ 61,786	$ 394,964
Less than 12 months, gross unrealized losses	(181)	(2,577)
12 months or longer, fair value	1,390	48,903
12 months or longer, gross unrealized losses	(15)	(980)
Total, fair value	63,176	443,867
Total, gross unrealized losses	(196)	(3,557)
US Treasury Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value		8,004
Less than 12 months, gross unrealized losses		(2)
12 months or longer, fair value		0
12 months or longer, gross unrealized losses		0
Total, fair value		8,004
Total, gross unrealized losses	0	(2)
Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value		59,197
Less than 12 months, gross unrealized losses		(148)
12 months or longer, fair value		0
12 months or longer, gross unrealized losses		0
Total, fair value		59,197
Total, gross unrealized losses	0	(148)
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	61,786	327,263
Less than 12 months, gross unrealized losses	(181)	(2,427)
12 months or longer, fair value	398	47,911
12 months or longer, gross unrealized losses	(6)	(970)
Total, fair value	62,184	375,174
Total, gross unrealized losses	(187)	(3,397)
Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, fair value	0	500
Less than 12 months, gross unrealized losses	0	0
12 months or longer, fair value	992	992
12 months or longer, gross unrealized losses	(9)	(10)
Total, fair value	992	1,492
Total, gross unrealized losses	$ (9)	$ (10)