Investment Securities (Disclosure Regarding Length of Time on Securities Available for Sale with Temporary Impairment) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair value	$ 106,577	$ 89,295
Less than 12 months, Gross unrealized losses	(362)	(279)
12 months or longer, Fair value	54,204	211,679
12 months or longer, Gross unrealized losses	(505)	(2,951)
Total, Fair value	160,781	300,974
Total, Gross unrealized losses	(867)	(3,230)
US Treasury Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair value		5,937
Less than 12 months, Gross unrealized losses		(3)
12 months or longer, Fair value		0
12 months or longer, Gross unrealized losses		0
Total, Fair value		5,937
Total, Gross unrealized losses	0	(3)
Agency Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair value	8,092	24,404
Less than 12 months, Gross unrealized losses	(4)	(40)
12 months or longer, Fair value	0	5,010
12 months or longer, Gross unrealized losses	0	(23)
Total, Fair value	8,092	29,414
Total, Gross unrealized losses	(4)	(63)
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair value	97,490	55,488
Less than 12 months, Gross unrealized losses	(350)	(221)
12 months or longer, Fair value	54,204	206,669
12 months or longer, Gross unrealized losses	(505)	(2,928)
Total, Fair value	151,694	262,157
Total, Gross unrealized losses	(855)	(3,149)
Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair value	995	3,466
Less than 12 months, Gross unrealized losses	(8)	(15)
12 months or longer, Fair value	0	0
12 months or longer, Gross unrealized losses	0	0
Total, Fair value	995	3,466
Total, Gross unrealized losses	$ (8)	$ (15)