Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended			6 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2011	Dec. 31, 2011	Mar. 31, 2011 Share Repurchase Program Expire In August 2012	Dec. 31, 2010 Share Repurchase Program Expire in May 2011 [Member]	Mar. 31, 2012 Minimum [Member]	Mar. 31, 2012 Maximum [Member]
Stockholders Equity Note [Line Items]
Outstanding stock options, exercise prices range, lower limit								$ 11.37	$ 26.29
Outstanding Nonvested stock awards, grant prices range, lower limit	$ 11.37
Outstanding Nonvested stock awards, grant prices range, upper limit	$ 26.31
Outstanding Performance restricted stock units, threshold stock price	$ 26.00
Antidilutive common shares not included in the computation of dilutive earnings per share	2,200,000		1,900,000
Authorized repurchase of common stock, value						$ 1,000.0	$ 500.0
Treasury Stock Acquired, Shares	7,500,000	600,000	7,100,000	7,700,000	17,700,000
Common stock repurchased	175.2		200.0		419.9
Shares repurchased cost, Commissions	0.2				0.3
Stock Repurchase Program Remaining Authorized Repurchase Amount	$ 349.7
Treasury Stock Shares Retired			7,700,000
Preferred stock, authorized	25,000,000
Preferred stock, par value	$ 0.10
Preferred stock, issued	0