Offsetting Derivative Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 10,850	$ 28,902
Gross Amounts of Recognized Financial Assets Set Off in the Balance Sheet	8,380	15,827
Derivative cash Collateral Pledged, Right to Receive Cash	0	0
Net Amounts of Liabilities Presented in the Balance Sheet	2,470	13,075
Gross Amounts Not Offset in the Balance Sheet, Financial Instruments	521	10,847
Gross Amounts Not Offset in the Balance Sheet, Cash Collateral Pledged	0	0
Net Amount	1,949	2,228
Fair Value of Financial Instruments Pledged as Collateral Not Set Off in the Balance Sheet	1,417	16,440
Derivatives
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	10,850	28,902
Gross Amounts of Recognized Financial Assets Set Off in the Balance Sheet	8,380	15,827
Derivative cash Collateral Pledged, Right to Receive Cash	0	0
Net Amounts of Liabilities Presented in the Balance Sheet	2,470	13,075
Gross Amounts Not Offset in the Balance Sheet, Financial Instruments	521	10,847
Gross Amounts Not Offset in the Balance Sheet, Cash Collateral Pledged	0	0
Net Amount	1,949	2,228
Fair Value of Financial Instruments Pledged as Collateral Not Set Off in the Balance Sheet	$ 1,417	$ 16,440