Stock Based Compensation Roll Forward Schedule of Stock Option Plan by Shares and Weighted Average Exercise Prices (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) plan $ / shares shares	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015 shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of compensation plans | plan	2
Expiration period (in years)	10 years
Award vesting period (in years)	4 years
Roll Forward of Shares Outstanding [Roll Forward]
Outstanding, Beginning Balance, in shares	366,329
Granted, in shares	55,621	58,349.5	58,975.431
Exercised, in shares	(58,804)
Forfeited, in shares	(16,991)
Outstanding, Ending Balance, in shares	346,155.000	366,329
Exercisable at December 31, 2017, in shares	225,694
Vested and Expected to Vest, in shares	120,461
Roll Forward of Shares Outstanding - Weighted Average Exercise Price: [Roll Forward]
Outstanding, Beginning Balance, in Weighted Average Exercise Price, | $ / shares	$ 21.86
Granted, in Weighted Average Exercise Price | $ / shares	36.12
Exercised, in Weighted Average Exercise Price | $ / shares	20.25
Forfeited, in Weighted Average Exercise Price | $ / shares	28.27
Outstanding, Ending Balance, in Weighted Average Exercise Price, | $ / shares	24.12	$ 21.86
Exercisable at December 31, 2017, in Weighted Average Exercise Price | $ / shares	21.61
Vested and Expected to Vest, in Weighted Average Exercise Price | $ / shares	$ 28.80
Outstanding at December 31, 2017, Weighted Average Remaining Contractual Life, in years	5 years 1 month 10 days
Exercisable at December 31, 2017, Weighted Average Remaining Contractual Life, in years	3 years 6 months 15 days
Vested and Expected to Vest, at December 31, 2017, Outstanding, Weighted Average Remaining Contractual Term	8 years 18 days
Weighted Average Expected Vesting Period, In Years	2 years 7 months 2 days	2 years 8 months 15 days	2 years 1 month 15 days
Outstanding at December 31, 2017, Aggregate Intrinsic Value | $	$ 3,403
Exercisable at December 31, 2017, Aggregate Intrinsic Value | $	2,785
Vested and Expected to Vest, Aggregate Intrinsic Value | $	$ 618
Shares Available for Grant at Period End, in shares	340,178