Stock Compensation - RSU and PSU award activity (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2014	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Stock Compensation Plans
Stock compensation expense		$ 21,300	$ 17,600	$ 42,100	$ 35,200
Other than options, disclosures
Assumed annualized forfeiture rate (as a percent)				5.00%
Stock compensation expense		$ 21,300	$ 17,600	$ 42,100	$ 35,200
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
Additional authorization (in shares)				1,000,000
Granted (in shares)				(325,651)
Cancelled (in shares)				23,789
Shares Available for Grant Ending Balance (in shares)		1,534,519		1,534,519
Shares Subject to Outstanding Options, Shares
Outstanding at the beginning of the period (in shares)				565,567
Granted (in shares)				325,651
Cancelled (in shares)				(23,789)
Released (in shares)				(7,278)
Outstanding at the end of the period (in shares)		858,203		858,203
Shares Subject to Outstanding Options, Weighted Average Exercise Price
Granted (in dollars per share)				$ 86.84
Cancelled (in dollars per share)				70.84
Released (in dollars per share)				$ 78.49
Weighted-average fair value assumptions
Cliff vesting period				3 years
Other than options, disclosures
Granted (in shares)				325,651
Outstanding (in shares)		1,534,519		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%