Stock-Based Compensation Long-Term Performance Restricted Stock Unit Award Monte Carlo Pricing Model Assumptions (Details) (Restricted Stock Units (RSUs) [Member], USD $)	6 Months Ended				3 Months Ended	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013 Long Term Performance Restricted Stock Award [Member]	Jun. 30, 2013 Long Term Performance Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield					0.00%	0.00%
Expected volatility					39.10%	39.10%
Risk-free interest rate					0.30%	0.30%
Expected term (years)					2 years 6 months 10 days	2 years 6 months 10 days
Weighted-average fair value	$ 42.51	[1]	$ 47.33	[1]	$ 45.70	$ 45.03

[1] Restricted stock units granted in 2012 and 2013 do not include awards under the Performance Award Agreement for the respective years, as these awards are not granted until final attainment of performance goals has been determined at the conclusion of the performance period, which had not occurred as of June 30, 2012 and 2013, respectively.