Fair Value Measurements - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Fair Value Measurements [Line Items]
Fair Value, Equity, Level 1 to Level 2 Transfers, Amount	$ 0	$ 0
Fair Value, Equity, Level 2 to Level 1 Transfers, Amount	$ 0	$ 0