Derivative Financial Instruments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Derivative [Line Items]
Notional amount	$ 539.5	$ 464.5
Fixed Interest Swap [Member]
Derivative [Line Items]
Notional amount	39.5	39.5
Variable Interest Rate Swap [Member]
Derivative [Line Items]
Notional amount	500.0	425.0
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional amount	22.2	10.5
Forward Commitments [Member]
Derivative [Line Items]
Notional amount	32.8	17.2
Customer Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	457.5	436.8
Offsetting Counter Party Derivative Instrument [Member]
Derivative [Line Items]
Notional amount	$ 457.5	$ 436.8