Stock-Based Compensation Plans (Options Plans) (Details) - Stock Options	3 Months Ended	9 Months Ended
	Sep. 30, 2018 $ / shares shares	Sep. 30, 2018 $ / shares shares
Shares
Beginning balance (in shares) | shares	2,290,893	2,285,703
Granted (in shares) | shares	2,580	377,472
Exercised (in shares) | shares	(163,702)	(504,674)
Canceled (in shares) | shares	(51,467)	(80,197)
Ending balance (in shares) | shares	2,078,304	2,078,304
Options exercisable at end of period (in shares) | shares	1,270,019	1,270,019
Weighted Average Exercise Price
Beginning balance (in USD per share) | $ / shares	$ 103.11	$ 83.73
Granted (in USD per share) | $ / shares	231.98	192.28
Exercised (in USD per share) | $ / shares	75.13	71.63
Canceled (in USD per share) | $ / shares	139.87	130.87
Ending balance (in USD per share) | $ / shares	104.57	104.57
Options exercisable at end of period (in USD per share) | $ / shares	$ 78.32	$ 78.32