Stock Based Compensation (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Notes to Financial Statements [Abstract]
Percentage of eligible earnings to purchase common stock through the employee stock purchase plan	10.00%		10.00%
Discount on the average closing price for the employee stock purchase plan			5.00%
Stock Based Compensation Expense Table
Stock based compensation	$ 13,756,000	$ 10,439,000	$ 40,040,000	$ 30,143,000
Tax effect recognized in net income	4,814,000	3,654,000	14,014,000	10,550,000
Windfall tax benefit/(shortfall), net	2,075,000	9,009,000	7,632,000	19,975,000
Employee stock options granted during the period			560,350	531,100
Weighted average assumptions used to value option grants Table
Fair value per share ($)			$ 36.87	$ 30.19
Risk-free interest rate (%)			0.80%	0.77%
Expected option life (years)			5 years 3 months 9 days	5 years 3 months 27 days
Expected volatility (%)			36.20%	36.51%
Expected dividend yield (%)			0.57%	0.58%
Cash received from exercise of options			20,500,000	40,100,000
Restricted stock awards granted during period			357,240	358,807
Weighted average fair value per share of restricted stock awards granted during the period			$ 116.76	$ 95.1
Restricted stock awards vested during period			123,762
Weighted average grant date fair value per share			$ 63.65
Weighted average vest date fair value per share			$ 120.92
Shares of stock purchased during the period by participants in the employee stock purchase plan			15,458	17,410
Amount paid for stock purchased during the period by participants in the employee stock purchase plan			$ 1,800,000	$ 1,600,000