Stock-Based Compensation (Details 2) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock Options / Stock Appreciation Rights
Assumptions used in determining the fair value of the stock-based awards
Risk-free interest rate, minimum (as a percent)	1.30%	1.50%
Risk-free interest rate, maximum (as a percent)	1.60%	1.60%
Volatility, minimum (as a percent)	22.70%	34.40%
Volatility, maximum (as a percent)	33.10%	35.10%
Expected life		4 years 9 months 7 days
Number of Shares
Outstanding at beginning of year (in shares)	5,076
Options and SARs granted (in shares)	28
Options and SARs exercised (in shares)	(946)
Options and SARs canceled (in shares)	(50)
Outstanding at end of period (in shares)	4,108
Exercisable at end of period (in shares)	2,187
Weighted Average Exercise Price
Outstanding at beginning of year (in dollars per share)	$ 17.38
Options and SARs granted (in dollars per share)	$ 43.66
Options and SARs exercised (in dollars per share)	$ 13.39
Options and SARs canceled (in dollars per share)	$ 24.68
Outstanding at end of period (in dollars per share)	$ 18.38
Exercisable at end of period (in dollars per share)	$ 14.11
Weighted average remaining contractual life of options and SARs outstanding, at end of period	6 years 7 months 17 days
Weighted average remaining contractual life of options and SARs exercisable, at end of period	5 years 2 months 9 days
Aggregate intrinsic value of options and SARs outstanding	$ 105,694
Aggregate intrinsic value of options and SARs exercisable	65,606
Additional disclosure about options and SARs
Closing price of stock (in dollars per share)	$ 44.11
Weighted average grant date fair value (in dollars per share)	$ 12.17	$ 10.34
Total intrinsic value of awards exercised	24,748	5,955
Stock Options / Stock Appreciation Rights | Minimum
Assumptions used in determining the fair value of the stock-based awards
Expected life	4 years 8 months 23 days
Expected dividend yield (as a percent)	0.00%
Stock Options / Stock Appreciation Rights | Maximum
Assumptions used in determining the fair value of the stock-based awards
Expected life	4 years 10 months 21 days
Expected dividend yield (as a percent)	1.50%
Options
Additional disclosure about options and SARs
Cash received from exercises	$ 5,000	$ 1,246