Share-Based Payments (Details 8) - $ / shares		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Time-vested restricted stock units
Weighted Average Exercise Price, Hemophilia spin-off adjustment		$ 0.00
Time-vested restricted stock units
Time-vested restricted stock units
Beginning Balance, Unvested, Shares		888,000
Beginning Balance, Weighted Average Grant Date Fair Value		$ 303.49
Shares, Hemophilia spin-off adjustment		12,000
Weighted Average Exercise Price, Hemophilia spin-off adjustment		$ 0.00
Shares, Granted	[1]	464,000
Weighted Average Grant Date Fair Value, Granted		$ 293.41	[1]	$ 268.52	$ 388.88
Shares, Vested		(350,000)
Weighted Average Grant Date Fair Value, Vested		$ 308.04
Shares, Forfeited		(182,000)
Weighted Average Grant Date Fair Value, Forfeited		$ 292.57
Ending Balance, Unvested, Shares		832,000		888,000
Ending Balance, Weighted Average Grant Date Fair Value		$ 291.85		$ 303.49

[1] RSUs granted in 2017 primarily represent RSUs granted in conjunction with our annual awards made in February 2017 and awards made in conjunction with the hiring of new employees. RSUs granted in 2017 also include approximately 11,000 RSUs granted to our Board of Directors.