Share-Based Payments (Details 4) - Market stock units - $ / shares		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Market stock units activity
Beginning Balance, Unvested, Shares		171,000
Beginning Balance, Weighted Average Grant Date Fair Value		$ 370.83
Shares, Granted	[1]	129,000
Weighted Average Grant Date Fair Value, Granted		$ 378.85	[1]	$ 382.59	$ 328.03
Shares, Vested		(91,000)
Weighted Average Grant Date Fair Value, Vested		$ 365.83
Shares, Forfeited		(29,000)
Weighted Average Grant Date Fair Value, Forfeited		$ 376.51
Ending Balance, Unvested, Shares		180,000		171,000
Ending Balance, Weighted Average Grant Date Fair Value		$ 371.32		$ 370.83

[1] MSUs granted during 2018 include awards granted in conjunction with our annual awards made in February 2018 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 2018 also reflect an adjustment based upon the final performance multiplier in relation to shares granted in 2017, 2016 and 2015.