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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
[Line Items]
Outstanding, beginning balance (in shares)				544	684
Outstanding, beginning balance, weighted average grant date fair value (in dollars per share)				$ 71.79
Granted (in shares)				212	209
Granted, weighted average grant date fair value (in dollars per share)				$ 97.96	$ 83.34
Forfeited (in shares)				(46)	(23)
Forfeited, weighted average grant date fair value (in dollars per share)				$ 77.79
Outstanding, ending balance (in shares)		422	532	422	532
Outstanding, ending balance, weighted average grant date fair value (in dollars per share)		$ 85.75		$ 85.75
Vested and Released [Member]
[Line Items]
Released (in shares)	[1]			(288)	(338)
Released, weighted average grant date fair value (in dollars per share)				$ 70.20
Released, aggregate intrinsic value				$ 28,494	$ 21,947
Vested but Not Released [Member]
[Line Items]
Released (in shares)				(10)
Released, aggregate intrinsic value				$ 733
Long Term Performance Restricted Stock Award [Member]
[Line Items]
Granted, weighted average grant date fair value (in dollars per share)		$ 0	$ 61.45	$ 113.75	$ 93.05

[1] (1)     Shares released is presented as gross shares and does not reflect shares withheld by us for employee payroll tax obligations.