Derivative Financial Instruments - Schedule of Weighted-Average Rates Paid and Received for Interest Rate Swaps Outstanding (Detail)	Sep. 30, 2014
Weighted Average Interest Rate Paid [Member]
Weighted Average Discount Rate [Line Items]
Fair value hedge loan/lease interest rate swaps	2.55%
Weighted Average Interest Rate Paid [Member] | Financial Institution Counterparties [Member]
Weighted Average Discount Rate [Line Items]
Non-hedging interest rate swaps – financial institution counterparties	4.06%
Weighted Average Interest Rate Paid [Member] | Customer Counterparties [Member]
Weighted Average Discount Rate [Line Items]
Non-hedging interest rate swaps – customer counterparties	1.69%
Weighted-Average Interest Rate Received [Member]
Weighted Average Discount Rate [Line Items]
Fair value hedge loan/lease interest rate swaps	0.15%
Weighted-Average Interest Rate Received [Member] | Financial Institution Counterparties [Member]
Weighted Average Discount Rate [Line Items]
Non-hedging interest rate swaps – financial institution counterparties	1.69%
Weighted-Average Interest Rate Received [Member] | Customer Counterparties [Member]
Weighted Average Discount Rate [Line Items]
Non-hedging interest rate swaps – customer counterparties	4.06%