Stock Compensation - RSU and PSU award activity (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended	9 Months Ended
	Jul. 31, 2016	Jan. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Stock Compensation Plans
Stock compensation expense			$ 26,500	$ 17,600		$ 68,600	$ 52,800
Other than options, disclosures
Assumed annualized forfeiture rate (as a percent)						5.00%
Stock compensation expense			$ 26,500	$ 17,600		$ 68,600	$ 52,800
Restricted Stock Units (RSUs)
Stock Compensation Plans
Number of shares awarded for each RSU (in shares)						1
Shares Available For Grant
Shares Available for Grant Beginning Balance (in shares)					834,433	834,433
Additional authorization (in shares)						1,000,000
Granted (in shares)						(708,426)
Cancelled (in shares)						32,880
Shares Available for Grant Ending Balance (in shares)			1,160,835			1,160,835
Shares Subject to Outstanding Options, Shares
Outstanding at the beginning of the period (in shares)					565,567	565,567
Granted (in shares)						708,426
Percentage of units vesting at the end of each calendar year (as a percent)	25.00%
Cancelled (in shares)						(32,880)
Released (in shares)						(7,278)
Outstanding at the end of the period (in shares)			1,231,887			1,231,887
Shares Subject to Outstanding Options, Weighted Average Exercise Price
Granted (in dollars per share)						$ 85.28
Cancelled (in dollars per share)						73.38
Released (in dollars per share)						$ 78.49
Weighted-average fair value assumptions
Vesting period	4 years				3 years
Other than options, disclosures
Granted (in shares)						708,426
Outstanding (in shares)			1,160,835		834,433	834,433
Released (in shares)						7,278
Restricted Stock Units (RSUs) | President And Chief Executive Officer
Shares Available For Grant
Shares Available for Grant Ending Balance (in shares)			266,667			266,667
Shares Subject to Outstanding Options, Shares
Granted (in shares)		400,000
Percentage of units vesting at the end of each calendar year (as a percent)						16.70%
Released (in shares)						(133,333)
Other than options, disclosures
Granted (in shares)		400,000
Outstanding (in shares)			266,667			266,667
Released (in shares)						133,333
Performance Stock Units (PSUs)
Stock Compensation Plans
Stock compensation expense						$ 0
Shares Available For Grant
Cancelled (in shares)						1,948
Shares Subject to Outstanding Options, Shares
Cancelled (in shares)						(1,948)
Shares Subject to Outstanding Options, Weighted Average Exercise Price
Cancelled (in dollars per share)						$ 64.55
Other than options, disclosures
Stock compensation expense						$ 0
Performance Stock Units (PSUs) | Maximum
Other than options, disclosures
Multiplier conversion rate of units into common stock (as a percent)						125.00%