Share-Based Payments (Details 5) - Market stock units - USD ($)	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Assumptions used in valuation of market based stock units
Expected dividend yield	0.00%		0.00%	0.00%
Minimum range of risk-free interest rates	0.90%		0.60%	0.20%
Maximum range of risk-free interest rates	1.60%		0.90%	1.00%
Average stock price on grant date minimum	$ 263.18		$ 260.67	$ 227.35
Average stock price on grant date maximum	$ 267.88		$ 304.86	$ 426.27
Weighted average grant date fair value	$ 382.59	[1]	$ 328.03	$ 493.43
Minimum
Assumptions used in valuation of market based stock units
Range of expected stock price volatility	33.00%		38.20%	31.00%
Maximum
Assumptions used in valuation of market based stock units
Range of expected stock price volatility	35.60%		40.70%	33.20%

[1] MSUs granted in 2017 include approximately 9,000 MSUs issued in 2017 based upon the attainment of performance criteria set for 2013, in relation to awards granted in that year. MSUs granted during 2017 also include awards granted in conjunction with our annual awards made in February 2017 and MSUs granted in conjunction with the hiring of employees. These grants reflect the target number of shares eligible to be earned at the time of grant. MSUs granted in 2017 reflect an adjustment based upon the final performance multiplier in relation to shares granted in 2016, 2015 and 2014.