Share Based Award (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock compensation and related tax benefits [Table Text Block]

	Year ended December 31,
	2014		2013		2012
Stock compensation expense	$	9,592	$	5,434	$	5,563
Tax benefit from stock-based compensation cost	$	3,567	$	2,052	$	1,922
Indirect tax benefit	$	209	$	866	$	209

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year ended December 31,
	2014			2013			2012
Number of time-based options granted	492,935			244,440			228,328
Grant date fair value of options granted (in thousands)	$	7,311		$	3,934		$	3,158
Weighted average assumptions for stock option valuation:
Expected term (years)	4.7			4.6			4.7
Expected stock price volatility	26.7		%	29.2		%	33.6		%
Risk-free interest rate	1.4		%	0.8		%	0.7		%
Expected dividend yield	—		%	—		%	—		%
Weighted average grant price per option	$	58.92		$	62.12		$	47.12
Weighted average grant date fair value per option	$	14.83		$	16.09		$	13.83

Schedule of Share-based compensation, performance stock option activity [Table Text Block]

Number of performance options granted	699,625
Grant date fair value of options granted (in thousands)	$	13,344
Weighted average assumptions for stock option valuation:
Expected term (years)	4.0
Expected stock price volatility	31.7		%
Risk-free interest rate	2.9		%
Expected dividend yield	—		%
Weighted average grant price per option	$	58.90
Weighted average grant date fair value per option	$	19.07

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

A summary of our stock option activity as of and for the year ended December 31, 2014 is as follows:

	Shares		Weighted Average Exercise Price Per Share		Weighted Average Contractual Life (Years)	Aggregate Intrinsic Value
Outstanding at December 31, 2013	1,952,124		$	39.26
Granted	1,192,560		$	58.91
Exercised	(529,181	)	$	32.78
Forfeited or expired	(58,567	)	$	52.51
Outstanding at December 31, 2014	2,556,936		$	49.46	7.0	$	82,936
Exercisable at December 31, 2014	1,193,223		$	39.19	4.7	$	50,963
Vested and expected to vest, December 31, 2014	2,556,936		$	49.46	7.0	$	82,936

Exercised Options Data [Table Text Block]

	Year ended December 31,
	2014		2013		2012
Intrinsic value of options exercised	$	18,802	$	21,847	$	12,211
Cash received from exercise of stock options	$	16,998	$	18,004	$	14,844
Tax benefit from stock option exercises	$	5,700	$	6,966	$	4,567

Schedule of restricted stock activity [Table Text Block]

	Year ended December 31,
	2014		2013		2012
PRSU
Shares granted			15,085		15,589
Grant date fair value per share			$	50.82	$	43.60
Grant date fair value			$	767	$	680
Intrinsic value vested	$	659	$	636
RSU
Shares granted	76,618		4,908		6,132
Grant date fair value per share	$	58.89	$	67.25	$	53.81
Grant date fair value	$	4,512	$	330	$	330
Intrinsic value vested	$	292	$	412

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

	Number of Units		Grant Date Fair Value Per Share		Weighted Average Contractual Life (Years)	Aggregate Intrinsic Value
Non-vested at December 31, 2013	25,692		$	48.12
Granted	76,618		$	58.89
Vested	(15,300	)	$	51.19
Forfeited	(978	)	$	43.60
Non-vested and expected to vest at December 31, 2014	86,032		$	57.22	1.0	$	7,046

Schedule of employee stock purchase plan (ESPP) [Table Text Block]

	Year ended December 31,
	2014			2013			2012
ESPP shares purchased by employees	47,466			50,944			61,004
Intrinsic value of ESPP purchases (in thousands)	$	476		$	840		$	913
Weighted average assumptions for ESPP valuation:
Expected term (in years)	0.5			0.5			0.5
Expected stock price volatility	20.8		%	24.4		%	23.6		%
Risk-free interest rate	1.1		%	0.1		%	0.1		%
Expected dividend yield	—		%	—		%	—		%