Stock-based Compensation Expense Fixed-Price Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Outstanding Shares,Beginning Balance (in shares)	1,316,733
Granted (in shares)	95,639	63,259	82,204
Exercised (in shares)	(161,909)
Forfeited (in shares)	(5,932)
Outstanding Shares, Ending Balance (in shares)	1,244,531	1,316,733
Exercisable, Ending Balance (in shares)	980,865
Weighted-Average Exercise Price
Outstanding Weighted-Average Exercise Price, Beginning Balance (in dollars per share)	$ 59.55
Granted (in dollars per share)	91.00
Exercised (in dollars per share)	29.73
Forfeited (in dollars per share)	95.47
Outstanding Weighted-Average Exercise (in dollars per share) Price, Ending Balance	65.67	$ 59.55
Exercisable Weighted-Average Exercise Price, Ending Balance (in dollars per share)	$ 59.47
Weighted-Average Remaining Contractual Term (Years)
Weighted-Averaged Remaining Contractual Term, Beginning Balance	4 years 2 months 12 days	4 years 3 months 18 days
Weighted-Averaged Remaining Contractual Term, Ending Balance	4 years 2 months 12 days	4 years 3 months 18 days
Exercisable Weighted-Average Remaining Contractual Term, Ending Balance	3 years 3 months 18 days
Aggregate Intrinsic Value
Outstanding Aggregate Intrinsic Value, Beginning Balance	$ 26,438
Outstanding Aggregate Intrinsic Value, Ending Balance	14,593	$ 26,438
Exercisable Aggregate Intrinsic Value, Ending Balance	$ 13,583