Stock-Based Compensation Restricted Stock Units Summary (Details) - Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		6 Months Ended
		Jun. 30, 2020	Jun. 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)		189	118
Granted, weighted average grant date fair value (in dollars per share)		$ 85.97	$ 56.40
Forfeited (in shares)		(13)	(36)
Forfeited, weighted average grant date fair value (in dollars per share)		$ 66.91
Outstanding, ending balance (in shares)		630	536
Outstanding, ending balance, weighted average grant date fair value (in dollars per share)		$ 70.74
Vested and Released [Member]
[Line Items]
Released (in shares)	[1]	(230)	(363)
Released, weighted average grant date fair value (in dollars per share)		$ 65.14
Released, aggregate intrinsic value		$ 2,506	$ 22,304
Vested but Not Released [Member]
[Line Items]
Released (in shares)		(8)
Released, aggregate intrinsic value		$ 534
Long Term Performance Restricted Stock Award [Member]
[Line Items]
Expected volatility		37.60%	31.30%
Risk-free interest rate		1.50%	2.50%
Expected term (years)		1 year 9 months 18 days	1 year 7 months 6 days
Granted, weighted average grant date fair value (in dollars per share)		$ 94.28	$ 60.91

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