Fair Value Measurement of Financial Assets and Liabilities - Additional Information (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 0
Level 3 assets	0	0
Level 3 liabilities	0	0
Derivatives	$ 0		$ 0