Earnings Per Share (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended		6 Months Ended
	Jul. 17, 2017	Jul. 31, 2016	Nov. 30, 2015	Jun. 30, 2017	Dec. 31, 2016
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Debt instrument				$ 4,408	$ 4,684
Common stock, date dividend declared				Jun. 21, 2017
Common stock, date dividend to be paid				Jul. 17, 2017
Common Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued		98,900,000
Price per share		$ 13.00
Proceeds from issuance of shares		$ 1,247
Series B Preferred Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Trading day period				20 days
Long-term Debt [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Debt instrument				$ 4,368	4,643
Long-term Debt [Member] | Term Loan 1 due December 2020 [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Payments on long-term debt		375
Debt instrument			$ 750	$ 327	$ 327
Debt instrument, term			3 years
Senior Notes [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Purchase of note principal		$ 700
Minimum [Member] | Depositary Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued upon conversion				1.85014
Minimum [Member] | Series B Preferred Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued upon conversion				37.0028
Potential number of shares issued upon conversion				63,829,830
Maximum [Member] | Depositary Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued upon conversion				2.17391
Maximum [Member] | Series B Preferred Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued upon conversion				43.4782
Potential number of shares issued upon conversion				74,999,895
Subsequent Event [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Common stock, shares issued as stock dividend	3,346,738