Derivative and Hedging Activities - Derivative Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	$ 101,027	$ 53,202
Subject to Master Netting Arrangements [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	9,981	3,197
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	5,621	1,535
Gross Amounts Not Offset in the Balance Sheet Cash Collateral Received, Derivative Assets	4,360	1,662
Net Amount, Derivative Assets	0	0
Subject to Master Netting Arrangements [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	9,938	3,178
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	5,578	1,516
Gross Amounts Not Offset in the Balance Sheet Cash Collateral Received, Derivative Assets	4,360	1,662
Net Amount, Derivative Assets	0	0
Subject to Master Netting Arrangements [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet		1
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets		1
Net Amount, Derivative Assets	0	0
Subject to Master Netting Arrangements [Member] | Equity Contracts [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	43	18
Gross Amounts Not Offset in the Balance Sheet Financial Instruments, Derivative Assets	43	18
Net Amount, Derivative Assets	$ 0	$ 0