Share-Based Compensation and Benefit Plans (Summary of Stock Options) (Details) - Stock option [Member] $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) d $ / shares shares	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015
Share-Based Compensation and Benefit Plans
Exercisable at the end of the year, average remaining contractual term	3 years 9 months 21 days	3 years 10 months 14 days	4 years 2 months 5 days
Employee stock option [Member]
Share-Based Compensation and Benefit Plans
Outstanding beginning balance, shares | shares	2,789
Outstanding at the beginning of the year, weighted-average exercise price | $ / shares	$ 105.11
Granted, shares | shares	282
Granted, weighted-average exercise price | $ / shares	$ 251.26
Exercised, shares | shares	(674)
Exercised, weighted-average exercise price | $ / shares	$ 48.58
Forfeited, shares | shares	(33)
Forfeited, weighted-average exercise price | $ / shares	$ 215.46
Outstanding ending balance, shares | shares	2,364	2,789
Outstanding at the end of the year, weighted-average exercise price | $ / shares	$ 137.08	$ 105.11
Outstanding at the end of the year, average remaining contractual term	5 years 3 months 18 days
Outstanding at the end of the year, aggregate intrinsic value | $	$ 244,562
Vested or expected to vest at the end of the year, shares | shares	2,319
Vested or expected to vest at the end of the year, weighted-average exercise price | $ / shares	$ 135.11
Vested or expected to vest at the end of the year, average remaining contractual term	5 years 2 months 26 days
Vested or expected to vest at the end of the year, aggregate intrinsic value | $	$ 244,492
Exercisable at the end of the year, shares | shares	1,571
Exercisable at the end of the year, weighted-average exercise price | $ / shares	$ 85.00
Exercisable at the end of the year, average remaining contractual term	3 years 9 months 21 days
Exercisable at the end of the year, aggregate intrinsic value | $	$ 244,360
Director [Member]
Share-Based Compensation and Benefit Plans
Outstanding beginning balance, shares | shares	11
Outstanding at the beginning of the year, weighted-average exercise price | $ / shares	$ 48.31
Granted, shares | shares	0
Granted, weighted-average exercise price | $ / shares	$ 0.00
Exercised, shares | shares	(11)
Exercised, weighted-average exercise price | $ / shares	$ 48.31
Forfeited, shares | shares	0
Forfeited, weighted-average exercise price | $ / shares	$ 0.00
Outstanding ending balance, shares | shares	0	11
Outstanding at the end of the year, weighted-average exercise price | $ / shares	$ 0.00	$ 48.31
Outstanding at the end of the year, average remaining contractual term, days | d	0
Outstanding at the end of the year, aggregate intrinsic value | $	$ 0
Vested or expected to vest at the end of the year, shares | shares	0
Vested or expected to vest at the end of the year, weighted-average exercise price | $ / shares	$ 0.00
Vested or expected to vest at the end of the year, average remaining contractual term, days | d	0
Vested or expected to vest at the end of the year, aggregate intrinsic value | $	$ 0
Exercisable at the end of the year, shares | shares	0
Exercisable at the end of the year, weighted-average exercise price | $ / shares	$ 0.00
Exercisable at the end of the year, average remaining contractual term, days | d	0
Exercisable at the end of the year, aggregate intrinsic value | $	$ 0