Stockholders' Deficit (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2015	Nov. 06, 2015
Class of Stock [Line Items]
Total capital stock, shares authorized	400,000,000
Common stock, shares authorized	300,000,000	300,000,000
Preferred stock, shares authorized	100,000,000	100,000,000
Common stock, par value per share	$ 0.01	$ 0.01
Preferred stock, par value per share	$ 0.01	$ 0.01
Preferred stock, shares outstanding	0
Maximum amount of dividends or stock repurchases permissible under the Credit Facility	$ 200
Open Market Repurchase Program for Common Stock, Adopted November 6, 2015 [Member]
Class of Stock [Line Items]
Maximum number of shares authorized for repurchase					10,000,000
Maximum value of shares authorized under repurchase program					$ 300
Number of shares repurchased and retired	0	0	0	532,188
Weighted-average price of repurchased and retired shares, per share				$ 27.31