Earnings Per Share (Schedule of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 51	[1]	$ 284	$ 259	[1]	$ 635
Mandatory convertible preferred stock dividend			27			54
Participating securities - mandatory convertible preferred stock			33	2		76
Net Income Attributable to Common Stock	$ 51		$ 224	$ 257		$ 505
Number of common shares: Weighted average outstanding	581,159,200		496,419,815	576,255,744		494,753,391
Number of common shares: Issued upon assumed exercise of outstanding stock options						3,317
Number of common shares: Effect of issuance of non-vested restricted common stock	480,580		761,311	683,562		707,576
Number of common shares: Effect of issuance of non-vested performance units	1,238,326		1,043,473	1,283,434		1,163,559
Number of common shares: Weighted average and potential dilutive outstanding	582,878,106		498,224,599	578,222,740		496,627,843
Earnings per common share: Basic	$ 0.09		$ 0.45	$ 0.45		$ 1.02
Earnings per common share: Diluted	$ 0.09		$ 0.45	$ 0.44		$ 1.02

[1] In 2018, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.