Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Stock option, shares
Cash received from stock option exercises			$ 14.5	$ 1.2
Stock-based compensation costs
Stock-based compensation expense	2.6	1.8	7.3	5.6
Income tax benefit	(1.0)	(0.7)	(2.7)	(2.1)
Stock-based compensation expense, net of income taxes	1.6	1.1	4.6	3.5
Excess tax benefit from stock-based compensation	7.2		25.7	1.2
Restricted Stock
Restricted stock, shares
Balance at the beginning of the period (in shares)			109,602
Granted (in shares)			34,934
Restrictions lapsed (vested) (in shares)			(26,925)
Forfeited (in shares)			(600)
Balance at the end of the period (in shares)	117,011		117,011
Restricted stock activity, additional disclosure
Outstanding at the beginning of the period, Weighted-Average Grant Date Fair Value (in dollars per share)			$ 84.46
Granted, Weighted-Average Grant Date Fair Value (in dollars per share)			$ 150.64
Restrictions lapsed (vested), Weighted-Average Grant Date Fair Value (in dollars per share)			$ 104.41
Forfeited, Weighted-Average Grant Date Fair Value (in dollars per share)	$ 81.30		$ 81.30
Outstanding at the end of the period, Weighted-Average Grant Date Fair Value (in dollars per share)	$ 99.64		$ 99.64
Stock-based compensation costs
Pre-tax unrecognized compensation cost, net of estimated forfeitures	6.9		6.9
Weighted-average period over which expense will be recognized (in years)			2.1
Stock Options
Stock option, shares
Outstanding at the beginning of the period (in shares)			1,737,062
Granted (in shares)			124,810
Exercised (in shares)			(585,600)
Forfeited (in shares)			(4,883)
Outstanding at the end of the period (in shares)	1,271,389		1,271,389
Exercisable balance at the end of the period (in shares)	959,741		959,741
Cash received from stock option exercises			14.5
Stock option activity, additional disclosure
Outstanding at the beginning of the period, Weighted-Average Exercise Price (in dollars per share)			$ 36.14
Granted, Weighted-Average Exercise Price (in dollars per share)	$ 151.39		$ 151.39
Exercised, Weighted-Average Exercise Price (in dollars per share)	$ 24.68		$ 24.68
Forfeited, Weighted-Average Exercise Price (in dollars per share)	$ 88.66		$ 88.66
Outstanding at the end of the period, Weighted-Average Exercise Price (in dollars per share)	$ 52.53		$ 52.53
Exercisable balance at the end of the period, Weighted-Average Exercise Price (in dollars per share)	$ 34.52		$ 34.52
Aggregate Intrinsic Value
Balance at the beginning of the period, Aggregate Intrinsic Value			172.0
Exercised			72.3
Balance at the end of the period, Aggregate Intrinsic Value	93.7		93.7
Exercisable balance at the end of the period, Aggregate Intrinsic Value	85.4		85.4
Stock-based compensation costs
Pre-tax unrecognized compensation cost, net of estimated forfeitures	12.4		12.4
Weighted-average period over which expense will be recognized (in years)			2.3
TNCLP | Phantom units
Stock-based compensation costs
Stock-based compensation expense	$ 0.3		$ 0.7