Stock-Based Compensation (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Stock options, shares
Cash received from stock option exercises			$ 12.6	$ 14.5
Stock-based compensation costs
Stock-based compensation expense	2.9	2.6	8.0	7.3
Income tax benefit	(1.1)	(1.0)	(3.0)	(2.7)
Stock-based compensation expense, net of income taxes	1.8	1.6	5.0	4.6
Excess tax benefit from stock-based compensation	14.6	7.1	30.0	25.7
Stock Options
Stock options, shares
Outstanding at the beginning of the period (in shares)			1,215,083
Granted (in shares)			130,670
Exercised (in shares)			(484,788)
Forfeited (in shares)			(6,762)
Outstanding at the end of the period (in shares)	854,203		854,203
Exercisable balance at the end of the period (in shares)	558,920		558,920
Cash received from stock option exercises			12.6
Stock option activity, additional disclosure
Outstanding at the beginning of the period, Weighted-Average Exercise Price (in dollars per share)			$ 53.95
Granted, Weighted-Average Exercise Price (in dollars per share)			$ 207.11
Exercised, Weighted-Average Exercise Price (in dollars per share)			$ 26.29
Forfeited, Weighted-Average Exercise Price (in dollars per share)			$ 112.29
Outstanding at the end of the period, Weighted-Average Exercise Price (in dollars per share)	$ 92.62		$ 92.62
Exercisable balance at the end of the period, Weighted-Average Exercise Price (in dollars per share)	$ 59.52		$ 59.52
Stock-based compensation costs
Pre-tax unrecognized compensation cost, net of estimated forfeitures	15.6		15.6
Weighted-average period over which expense will be recognized			2 years 3 months 18 days
Aggregate Intrinsic Value
Balance at the beginning of the period, Aggregate Intrinsic Value			111.4
Exercised			79.9
Balance at the end of the period, Aggregate Intrinsic Value	110.7		110.7
Exercisable balance at the end of the period, Aggregate Intrinsic Value	90.9		90.9
Restricted Stock
Restricted stock, shares
Balance at the beginning of the period (in shares)			112,571
Granted (in shares)			25,662
Vested (in shares)			(37,779)
Balance at the end of the period (in shares)	100,454		100,454
Restricted stock activity, additional disclosure
Outstanding at the beginning of the period, Weighted-Average Grant Date Fair Value (in dollars per share)			$ 100.83
Granted, Weighted-Average Grant Date Fair Value (in dollars per share)			$ 201.22
Vested, Weighted-Average Grant Date Fair Value (in dollars per share)			$ 95.35
Outstanding at the end of the period, Weighted-Average Grant Date Fair Value (in dollars per share)	$ 128.54		$ 128.54
Stock-based compensation costs
Pre-tax unrecognized compensation cost, net of estimated forfeitures	7.3		7.3
Weighted-average period over which expense will be recognized			2 years 1 month 6 days
Phantom units | TNCLP
Stock-based compensation costs
Stock-based compensation expense	$ 0.2		$ 0.8