Other Noninterest Expense - Additional Information (Detail) (USD $)	3 Months Ended			9 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Nonoperating expense [Line Items]
Other miscellaneous expenses	$ 6,821,000		$ 19,851,000	$ 25,105,000	$ 32,504,000
Expense related to the settlement of the assessment with the FDIC		10,300,000
Gain on Sale of Insurance Business				9,400,000
Sales price of divested business				15,500,000
Early termination fee of reverse repurchase obligations		3,500,000
Other Miscellaneous Expense [Member]
Nonoperating expense [Line Items]
Other miscellaneous expenses	1,100,000	7,300,000	12,600,000
Branch Closures [Member]
Nonoperating expense [Line Items]
Expense related to closure of branches	1,100,000	3,500,000
Number of branch locations		15
Branch Closures [Member] | Other Miscellaneous Expense [Member]
Nonoperating expense [Line Items]
Expense related to closure of branches		$ 2,900,000