Investment Securities (Credit Losses on Non-Agency Residential Mortgage-Backed Securities) (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Non-Agency Residential Mortgage-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Balance	$ 0	$ 1,026,000	$ 0	$ 768,000
Amount related to credit losses for which an other-than-temporary impairment was not previously recognized	0	0	0	325,000
Additional amount related to credit losses for which an other-than-temporary impairment was previously recognized	0	0	0	63,000
Realized losses	0	26,000	0	156,000
Balance	0	1,000,000	0	1,000,000
Other Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Balance	609,000	609,000	609,000	512,000
Amount related to credit losses for which an other-than-temporary impairment was not previously recognized	0	0	0	0
Additional amount related to credit losses for which an other-than-temporary impairment was previously recognized	0	0	0	97,000
Realized losses	0	0	0	0
Balance	$ 609,000	$ 609,000	$ 609,000	$ 609,000