Stock-Based Compensation, Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Stock Options Shares Outstanding, Beginning balance (in shares)	[1]	5,281
Granted	[1]	1,050
Exercised	[1]	(418)
Forfeited or expired	[1]	(85)
June 30, 2019	[1]	5,828	5,281
June 30, 2019	[1]	3,631
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
December 31, 2018		$ 19.09
Granted		22.77
Exercised, Weighted Average Exercise Price		15.68
Forfeited		23.96
June 30, 2019		19.94	$ 19.09
Options Exercisable, Weighted Average Exercise Price (in usd per share)		$ 18.04
Stock Options Outstanding, Weighted Average Remaining Contractual Term		6 years 7 months 9 days	6 years 2 months 4 days
Options exercisable, Weighted Average Remaining Contractual Term		5 years 3 months 25 days
Stock Options Outstanding, Aggregate Intrinsic Value		$ 14,870	$ 12,392
Options exercisable, Aggregate Intrinsic Value		$ 14,016

[1] (a) In thousands