Stockholders Equity - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended
	Feb. 28, 2013	Mar. 31, 2013
Accelerated Share Repurchase Program
Stockholders' Equity [Line Items]
Repurchase of common stock, authorized value	$ 250
Stock repurchase, amount paid		250
Stock repurchase, shares delivered		5.5
Stock repurchase, amount recorded as treasury stock		225
Stock repurchase, amount recorded in additional paid in capital		25
Maximum
Stockholders' Equity [Line Items]
Repurchase of common stock, authorized value	$ 500