Common Stock, Preferred Stock and Equity Plans - Outstanding and Vested Stock Options (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock Options
Stock options outstanding at beginning of period (in shares)	12,642
Stock options granted (in shares)	2,359
Stock options exercised (in shares)	(4,561)
Stock options forfeited (in shares)	(611)
Stock options expired (in shares)	(62)
Stock options outstanding at end of period (in shares)	9,767	12,642
Stock options exercisable at end of period (in shares)	5,313
Weighted-average Exercise Price
Weighted-average exercise price outstanding at beginning of period (usd per share)	$ 81.41
Weighted average exercise price, granted (usd per share)	108.43
Weighted average exercise price, exercised (usd per share)	70.90
Weighted average exercise price, forfeited (usd per share)	99.53
Weighted average exercise price, expired (usd per share)	105.24
Weighted-average exercise price outstanding at end of period (usd per share)	91.57	$ 81.41
Weighted average exercise price exercisable at the end of the period (usd per share)	$ 80.14
Weighted-average Remaining Contractual Life
Weighted-average Remaining Contractual Life, outstanding (in years)	6 years 11 months 12 days
Weighted-average Remaining Contractual Life, exercisable (in years)	5 years 9 months
Aggregate Intrinsic Value
Aggregate intrinsic value, outstanding	$ 585,293
Aggregate intrinsic value, exercisable	375,472
Total intrinsic value of stock options exercised	302,800	$ 48,600	$ 252,900
Total cash received from employees as a result of employee stock option exercises	$ 323,300	$ 48,500	$ 165,600
Weighted Average
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market share price (usd per share)	$ 150.71