Share-Based Compensation and Benefit Plans (Employee Stock Purchase Plan) (Narrative) (Details) - Employee stock purchase plan [Member]	12 Months Ended
	Dec. 31, 2017 Rate
Share-Based Compensation and Benefit Plans
Other employee benefit plan descriptions	The Company’s employee stock purchase plan (the “ESPP”) permits eligible employees to purchase shares of the Company’s common stock at 85% of the fair market value. Employees may authorize the Company to withhold up to 5% of their annual salary to participate in the plan.
Employee stock purchase plan stock purchase percentage	85.00%