Derivative and Hedging Activities - Derivative Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	$ 43,049	$ 45,898
Subject to Master Netting Arrangement [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	2,375	2,296
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	641	995
Gross Amounts Not Offset in the Balance Sheet Cash Collateral Received, Derivative Assets	1,734	1,301
Net Amount, Derivative Assets	0	0
Subject to Master Netting Arrangement [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	1,867	2,109
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	519	810
Gross Amounts Not Offset in the Balance Sheet Cash Collateral Received, Derivative Assets	1,348	1,299
Net Amount, Derivative Assets	0	0
Subject to Master Netting Arrangement [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	491	140
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	105	138
Gross Amounts Not Offset in the Balance Sheet Cash Collateral Received, Derivative Assets	386	2
Net Amount, Derivative Assets	0	0
Subject to Master Netting Arrangement [Member] | Equity Contracts [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	17	47
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	17	47
Net Amount, Derivative Assets	$ 0	$ 0