Investment Securities (Narrative) (Detail) (USD $)	3 Months Ended			3 Months Ended				3 Months Ended
	Mar. 31, 2014 Securities	Dec. 31, 2013	Mar. 31, 2013	Mar. 31, 2014 Minimum [Member]	Mar. 31, 2014 Maximum [Member]	Mar. 31, 2014 Other Structured Financial Products [Member]	Mar. 31, 2013 Other Structured Financial Products [Member]	Mar. 31, 2014 Other Equity Securities [Member]	Mar. 31, 2013 Other Equity Securities [Member]
Investment [Line Items]
Amount of securities pledged to secure public funds and other purposes as required by law	$ 1,420,413,000	$ 1,512,824,000
Number of non-agency residential mortgage-backed securities that had unrealized losses	1
Number of non-agency residential mortgage-backed securities rated below investment grade	0
Number of non-agency residential mortgage-backed securities that have subprime or Alt-A components	0
Number of non-agency residential-mortgage backed securities with other-than-temporary impairment	0
Accumulated other comprehensive income (loss), other-than- temporarily impaired securities	0		745,000
Other than temporary impairment								609,000	512,000
Number of days mortgage is past due related to cumulative default rate				60 days	90 days
Unrealized loss						$ 13,619,000	$ 15,072,000