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
		Mar. 31, 2020	Mar. 31, 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)		182	107
Granted, weighted average grant date fair value (in dollars per share)		$ 87.17	$ 56.04
Forfeited (in shares)		(7)	(17)
Forfeited, weighted average grant date fair value (in dollars per share)		$ 67.42
Outstanding, ending balance (in shares)		667	591
Outstanding, ending balance, weighted average grant date fair value (in dollars per share)		$ 70.55
Vested and Released [Member]
[Line Items]
Released (in shares)	[1]	(192)	(316)
Released, weighted average grant date fair value (in dollars per share)		$ 65.08
Released, aggregate intrinsic value		$ 12,454	$ 19,074
Vested but Not Released [Member]
[Line Items]
Released (in shares)		(8)
Released, aggregate intrinsic value		$ 473
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.