Stock-Based Compensation Long-Term Performance Restricted Stock Unit Award Monte Carlo Pricing Model Assumptions (Details) (Restricted Stock Units (RSUs) [Member], USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value			$ 35.49	[1]	$ 42.51	[1]
Long Term Performance Restricted Stock Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%		0.00%
Expected volatility	34.00%	39.10%	32.40%		39.10%
Risk-free interest rate	0.60%	0.30%	0.40%		0.30%
Expected term (years)	2 years 6 months 30 days	2 years 6 months 10 days	2 years 0 months 0 days		2 years 6 months 10 days
Weighted-average fair value	$ 41.47	$ 45.70	$ 34.87		$ 45.03

[1] Restricted stock units granted in 2013 and 2014 do not include awards under the Performance Award Agreement for the respective years, as these awards are not granted until attainment of annual performance goals has been determined at the conclusion of the performance period, which had not occurred as of June 30, 2013 and 2014, respectively.