Stock Compensation - RSU and PSU award activity (Details)	3 Months Ended
	Mar. 31, 2017 $ / shares shares
Restricted Stock Units (RSUs)
Shares Available For Grant
Shares Available for Grant Beginning Balance (in shares)	1,146,152
Granted (in shares)	(68,782)
Cancelled (in shares)	15,341
Shares Available for Grant Ending Balance (in shares)	1,092,711
Shares Subject to Outstanding Options, Shares
Outstanding at the beginning of the period (in shares)	1,246,570
Granted (in shares)	68,782
Cancelled (in shares)	(15,341)
Released (in shares)	(163,354)
Outstanding at the end of the period (in shares)	1,093,281
Shares Subject to Outstanding Options, Weighted Average Exercise Price
Granted (in dollars per share) | $ / shares	$ 117.54
Cancelled (in dollars per share) | $ / shares	83.64
Released (in dollars per share) | $ / shares	$ 118.45
Performance Stock Units (PSUs)
Shares Subject to Outstanding Options, Shares
Released (in shares)	(43,376)
Shares Subject to Outstanding Options, Weighted Average Exercise Price
Released (in dollars per share) | $ / shares	$ 122.29