Derivative Instruments and Hedging Activities - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) Derivative Swap	Dec. 31, 2015 USD ($) Derivative Swap
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification adjustment from accumulated other comprehensive income	$ 2.6
Termination value of derivatives in a net liability position	23.3
Minimum collateral with counterparties	$ 22.8
Minimum
Derivative Instruments, Gain (Loss) [Line Items]
Derivative expiration period (days)	30 days
Maximum
Derivative Instruments, Gain (Loss) [Line Items]
Derivative expiration period (days)	60 days
Not Designated as Hedging Instrument | Residential mortgage loan commitments
Derivative Instruments, Gain (Loss) [Line Items]
Aggregate notional amount	$ 4.5	$ 2.8
Interest Rate Swaps | Derivative Designated as Cash Flow Hedges | Cash Flow Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Number of outstanding interest rate derivative | Derivative	1	1
Aggregate notional amount	$ 150.0	$ 150.0
Interest Rate Swaps | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Aggregate notional amount	$ 457.2	$ 461.0
Number of interest rate swaps | Swap	62	62
Credit Contract | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Aggregate notional amount	$ 36.3	$ 19.3