Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended																1 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 1999 Stock Incentive Plan 1999 [Domain]	Dec. 31, 2011 Stock Incentive Plan 2001 [Domain]	Dec. 31, 2001 Stock Incentive Plan 2001 [Domain]	Dec. 31, 2011 Stock Incentive Plan 2007[Member]	Dec. 31, 2007 Stock Incentive Plan 2007[Member]	Dec. 31, 2011 nonvestedstockawards [Domain]	Dec. 31, 2010 nonvestedstockawards [Domain]	Dec. 31, 2009 nonvestedstockawards [Domain]	Dec. 31, 2011 vestedstockawards [Domain]	Dec. 31, 2010 vestedstockawards [Domain]	Dec. 31, 2009 vestedstockawards [Domain]	Dec. 31, 2011 Cashsettledawards [Domain]	Dec. 31, 2010 Cashsettledawards [Domain]	Sep. 30, 2007 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2009 Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized				17,500,000		2,000,000		35,000,000
fullvalueaward2007plan								2.7
Award Vesting Period				3	three		3											three year
Number of Shares Available for Grant				250,000			18,250,000
Award Vesting Period, Maximum						ten		eight
Options, Grants in Period, Weighted Average Grant Date Fair Value									$ 26.13	$ 20.91	$ 12.32				$ 26.22	$ 20.79	$ 15.99	$ 11.73	$ 9.04	$ 4.45
Nonvested Awards, Total Compensation Cost Not yet Recognized									$ 11.5									$ 0.5
Weighted Average Remaining Contractual Term of Outstanding Options									0.7
Equity Instruments Other than Options, Grants in Period									715,000						85,000		1,250,000
Options, Exercises in Period, Total Intrinsic Value																		3.9	3.2	2.6
Equity Instruments Other than Options, Vested in Period, Total Fair Value												19.2	19.0	17.5	0.7			2.7	2.5	2.0
Cash Used to Settle Awards															0.9
Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition																		0.7
Fair Value Assumptions, Expected Volatility Rate																	29.00%	53.00%	55.00%	50.00%
Fair Value Assumptions, Expected Term																	4.4	5.5
Fair Value Assumptions, Expected Dividend Rate																	1.24%	1.41%	1.59%	1.68%
Fair Value Assumptions, Risk Free Interest Rate																	3.97%	2.37%	2.33%	1.89%
Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options	$ 14.8	$ 10.0	$ 8.0