Share-Based Compensation and Benefit Plans (Employee Stock Purchase Plan Activity) (Details) - Employee stock purchase plan [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-Based Compensation and Benefit Plans
Compensation expense for shares issued under the ESPP	$ 2,490	$ 2,285	$ 2,212
Income tax benefit from compensation expense for shares issued under the ESPP	$ 612	$ 566	$ 844
Shares awarded or issued under employee benefit plans, shares	43	53	64
Weighted-average grant-date fair value of shares issued during the period in compensation and benefit plans other than stock options	$ 329.69	$ 245.26	$ 196.72