Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Common Stock, Dividends, Per Share, Declared	$ 0.13	$ 0.39
Payments of dividends (in dollars per share)		$ 179,200,000	$ 0
Distributable Reserves	$ 9,500,000,000	9,500,000,000
Stock repurchase program, authorized amount	$ 500,000,000	$ 500,000,000
Shares repurchased (in shares)		12.3
Shares repurchased, value		$ 384,200,000