Equity Equity (Dividends) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended								12 Months Ended			102 Months Ended
	Dec. 07, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Cash Paid		$ 0.13	$ 0.13	$ 0.13	$ 0.13
Dividends declared on common stock (per share amount)	$ 0.1365	$ 0.27	$ 0.13	$ 0	$ 0.13	$ 0.25	$ 0.12	$ 0	$ 0.12	$ 0.53	$ 0.49	$ 0.45
Treasury Stock, Value, Acquired, Cost Method													$ 1,900
Payments for Repurchase of Common Stock										$ 0	$ 0	$ 79
Acquisition of treasury stock (shares)										0			154,300,000
Treasury Stock Acquired, Average Cost Per Share													$ 12.12
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 264								$ 264			$ 264
Treasury stock, shares (in shares)		154,905,595				155,924,785				154,905,595	155,924,785		154,905,595