Share-based Compensation Stock Options (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	1 year 296 days
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	$ 8,340
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant-date fair value per share	$ 56.15	$ 41.52	$ 35.69
Expected term (years)	6 years 3 months	6 years 3 months	6 years 3 months
Risk-free interest rate	1.00%	1.00%	1.15%
Expected volatility	63.73%	66.80%	70.71%
Award vesting period	4 years
Contractual Term	10 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period, shares	510
Outstanding at beginning of period, price	$ 35.54
Granted, shares	74
Granted, price	$ 93.34
Exercised	(23)
Exercised, price	$ 33.84
Expired or forfeited, shares	(9)
Expired or forfeited, price	$ 59.53
Outstanding at end of period, shares	552	510
Outstanding at end of period, price	$ 42.92	$ 35.54
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	4,040
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	5 years 340 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	547
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 42.61
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	4,040
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term	5 years 332 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	344
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 26.85
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	4,040
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	4 years 285 days
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	2 years 92 days
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	2,302
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	940	21,199	18,310
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value	$ 3,163	$ 2,673	$ 2,216