FDIC loss share (expense) income - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended	3 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Federal Deposit Insurance Corporation [Member]
F D I C Loss Share Expense Income [Line Items]
Loss Sharing Agreement Allocation Percentage		80.00%
Estimated Credit Losses	$ 102.9
Remaining Life Of All Loan Pools Covered	six years
Indemnification Asset Remaining Life For Commercial Construction Consumer Loans	one year
Indemnification Asset Remaining Life For Single Family Mortgage Loans	six years