Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended			3 Months Ended		12 Months Ended			3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jun. 30, 2011 Accelerated share repurchase program [Member]	Mar. 31, 2011 Accelerated share repurchase program [Member]	Dec. 31, 2012 Accelerated share repurchase program [Member]	Dec. 31, 2011 Accelerated share repurchase program [Member]	Dec. 31, 2010 Accelerated share repurchase program [Member]	Jun. 30, 2012 Share Repurchase Program Expire In January 2014 [Member]	Mar. 31, 2011 Share Repurchase Program Expire In August 2012 [Member]	Jun. 30, 2010 Share Repurchase Program Expire in May 2011 [Member]
Stockholders Equity Note [Line Items]
Stock Repurchase Program, Authorized Amount									$ 750.0	$ 1,000.0	$ 500.0
Stock Repurchase Program Remaining Authorized Repurchase Amount	550.0
Shares repurchased cost, Commissions	0.6	0.3	0.3
Stock Repurchased and Retired During Period, Shares				600,000	7,100,000	0	7,700,000	0
Treasury Stock, Value, Acquired, Cost Method					$ 200.0
Preferred stock, authorized	25,000,000
Preferred stock, par value	$ 0.10
Preferred stock, issued	0
Oustanding Stock Options, grant price range, lower limit	$ 11.37
Oustanding Stock Options, grant price range, upper limit	$ 26.29
Outstanding Nonvested stock awards, grant prices range, lower limit	$ 19.38
Outstanding Nonvested stock awards, grant prices range, upper limit	$ 26.31
Antidilutive common shares not included in the computation of dilutive earnings per share	2,500,000	2,100,000	3,500,000