Derivative Instruments and Hedging Activities - Balance Sheet Offsetting Disclosure (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Offsetting [Abstract]
Gross Amount of Recognized Assets	$ 32
Gross Amount Offset in the Statement of Financial Position, Derivative Assets
Net Amount of Assets Presented in the Statement of Financial Position	32
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments, Derivative Assets	32
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received, Derivative Assets
Derivative Assets, Net Amount
Gross Amount of Recognized Liabilities	44	353
Gross Amount Offset in the Statement of Financial Position, Derivative Liabilities
Net Amount of Liabilities Presented in the Statement of Financial Position	44	353
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments, Derivative Liabilities	44	353
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received, Derivative Liabilities
Derivative liabilities, Net Amount