Derivative and Hedging Activities - Derivative Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	$ 43,319	$ 46,160
Subject to Master Netting Arrangement [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	42,812	45,985
Gross Amount Not Offset in the Balance Sheet Financial Instruments, Derivative Liabilities	26,662	30,976
Gross Amount Not Offset in the Balance Sheet Cash Collateral Pledged, Derivative Liabilities	14,388	13,243
Net Amount, Derivative Liabilities	1,762	1,766
Subject to Master Netting Arrangement [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	1,869	2,330
Gross Amount Not Offset in the Balance Sheet Financial Instruments, Derivative Liabilities	1,869	2,330
Subject to Master Netting Arrangement [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheet	40,943	43,655
Gross Amount Not Offset in the Balance Sheet Financial Instruments, Derivative Liabilities	24,793	28,646
Gross Amount Not Offset in the Balance Sheet Cash Collateral Pledged, Derivative Liabilities	14,388	13,243
Net Amount, Derivative Liabilities	$ 1,762	$ 1,766