Stock-Based Compensation Restricted Stock Units Summary (Details) - Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
[Line Items]
Outstanding, beginning balance (in shares)				684	817
Outstanding, beginning balance, weighted average grant date fair value (in dollars per share)				$ 64.38
Granted (in shares)				209	334
Granted, weighted average grant date fair value (in dollars per share)				$ 83.34	$ 62.04
Forfeited (in shares)				(23)	(53)
Forfeited, weighted average grant date fair value (in dollars per share)				$ 69.12
Outstanding, ending balance (in shares)		532	663	532	663
Outstanding, ending balance, weighted average grant date fair value (in dollars per share)		$ 71.45		$ 71.45
Vested and Released [Member]
[Line Items]
Released (in shares)	[1]			(338)	(435)
Released, weighted average grant date fair value (in dollars per share)				$ 65.01
Released, aggregate intrinsic value				$ 21,947	$ 26,852
Vested but Not Released [Member]
[Line Items]
Released (in shares)				(9)
Released, aggregate intrinsic value				$ 549
Long Term Performance Restricted Stock Award [Member]
[Line Items]
Granted, weighted average grant date fair value (in dollars per share)		$ 61.45	$ 72.18	$ 93.05	$ 61.25

[1] (1)     Shares released is presented gross of shares netted for employee payroll tax obligations.