Shared Based Awards (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock compensation	$ 5,563,000	$ 4,016,000	$ 3,471,000
Tax benefit from stock-compensation cost	1,922,000	1,376,000	1,153,000
Indirect tax benefit from stock options	209,000	785,000	438,000
Stock option activity [Abstract]
Outstanding, Weighted Average Contractual Life (years)	4 years 8 months
Exercisable, Weighted Average Contractual Life (years)	3 years 6 months
Vested and Expect to Vest, Weighted Average Contractual Life (years)	4 years 8 months
Intrinsic value [Abstract]
Intrinsic value of stock options exercised	12,211,000	11,451,000	4,422,000
Proceeds from Stock Options Exercised	14,844,000	7,974,000	2,517,000
Tax benefits from exercise of stock options	4,567,000	4,288,000	1,680,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Performance restricted stock units issued	15,589
Performance restricted stock award value	43.60
Performance stock award earned	31,178
Restricted Stock Units Granted	6,132
Restricted Stock Units fair value	$ 53.81
ESPP [Abstract]
Shares available employee stock purchase plan	320,849
Stock Issued During Period, Value, Employee Stock Purchase Plan	2,220,000	1,828,000	1,576,000
Stock Option [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unamortized stock compensation expense	6,500,000
Unamortized stock compensation	1 year 3 months
Employee Stock [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unamortized stock compensation expense	100,000
Share awards - initial authorized for issuance [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Authorized share in stock incentive plan	650,000
Share awards - total available for issuance [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Authorized share in stock incentive plan	1,650,363
Share awards available for issuance adjustment [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Authorized share in stock incentive plan	250,363
Stock Options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Number of Options Granted	228,328	290,000	243,000
Weighted average grant date fair value	$ 13.83	$ 14.10	$ 10.18
Stock option activity [Abstract]
Outstanding options, shares	2,745,428
Outstanding options, weighted average exercise price	$ 33.28
Granted options, shares	228,328
Granted options, weighted average exercise price	$ 47.12	$ 43.27	$ 34.70
Exercised options, shares	(526,040)
Exercised options, weighted average exercise price	$ 28.22
Forfeited options, shares	(2,963)
Forfeited options, weighted average exercise price	$ 34.12
Outstanding options, shares	2,444,753	2,745,428
Outstanding options, weighted average exercise price	$ 35.66	$ 33.28
Outstanding, Aggregate intrinsic value	61,778,000
Exercisable options, shares	1,670,325
Exercisable options, weighted average exercise price	$ 34.66
Exercisable, Intrinsic value of stock options	43,873,000
Vested and Expected to Vest, shares	2,444,753
Vested and Expect to Vest Weighted Average Exercise Price Per Share	$ 35.66
Vested and Expected to Vest, Aggregate intrinsic value	61,778,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Stock options granted, value	3,158,000	4,090,000	2,474,000
ESPP [Abstract]
Expected term (in years)	4 years 8 months	5 years 0 months	3 years 5 months
Expected stock price volatility	33.60%	34.50%	40.20%
Risk-free interest rate	0.70%	1.70%	0.80%
Expected dividend yield	0.00%	0.00%	0.00%
Restricted Stock and Performance Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Restricted Stock Units, number	0
Restricted Stock Units Granted	37,310
Restricted Stock Units Vested	0
Restricted Stock Units Forfeited	0
Restricted Stock Units, number	37,310
Restricted Stock Units, Nonvested, Weighted Average Remaining Contractual Terms	1 year
Restricted Stock Units, Nonvested, Intrinsic Value	$ 2,273,000
Employee Stock [Member]
ESPP [Abstract]
Employee stock purchase plan, shares issued	61,004	57,643	53,739
Stock Issued During Period, Value, Employee Stock Purchase Plan	$ 913,000	$ 530,000	$ 278,000
Expected term (in years)	0 years 6 months	0 years 6 months	0 years 6 months
Expected stock price volatility	23.60%	26.00%	26.50%
Risk-free interest rate	0.10%	0.40%	0.20%
Expected dividend yield	0.00%	0.00%	0.00%