Contingencies - Additional Information (Detail) (USD $) In Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2011	Mar. 31, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Loss Contingencies [Line Items]
Charge related to resolution of investigation	$ 0	$ 500	$ 0	$ 500	$ 0