Derivative Instruments - Derivative Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	$ 53,202	$ 45,898
Subject to Master Netting Arrangement [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	3,197	2,296
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	1,535	995
Gross Amounts Not Offset in the Balance Sheet Cash Collateral Received, Derivative Assets	1,662	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	3,178	2,109
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	1,516	810
Gross Amounts Not Offset in the Balance Sheet Cash Collateral Received, Derivative Assets	1,662	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	1	140
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	1	138
Gross Amounts Not Offset in the Balance Sheet Cash Collateral Received, Derivative Assets		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	18	47
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	18	47
Net Amount, Derivative Assets	$ 0	$ 0