Share-Based Compensation and Benefit Plans (Other Share-Based Compensation Activity) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Employee stock purchase plan [Member]
Share-Based Compensation and Benefit Plans
Compensation expense for share-based compensation	$ 632	$ 577	$ 1,209	$ 1,120
Income tax benefit from compensation expense for share-based compensation	157	143	301	279
Restricted stock [Member]
Share-Based Compensation and Benefit Plans
Compensation expense for share-based compensation	348	351	687	692
Income tax benefit from compensation expense for share-based compensation	$ 86	$ 87	$ 171	$ 172