Earnings Per Share (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended					9 Months Ended		12 Months Ended
	Oct. 17, 2016	Sep. 30, 2016	Jul. 31, 2016	Nov. 30, 2015	Jan. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Payments on long-term debt							$ 1,175	$ 500
Debt instrument		$ 4,685					$ 4,685		$ 4,733
Bridge Loan [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Bridge loan					$ 4,500	$ 4,500			$ 4,500
Debt instrument, term					364 days	364 days			364 days
Common Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued			98,900,000		30,000,000
Price per share			$ 13.00		$ 23.00
Proceeds from issuance of shares			$ 1,247		$ 669
Depositary Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued					34,500,000
Proceeds from issuance of shares					$ 1,700
Depositary shares conversion rate					5.00%
Liquidation preference per share					$ 50
Series B Preferred Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Liquidation preference per share		$ 1,000			$ 1,000		$ 1,000		$ 1,000
Trading day period							20 days
Long-term Debt [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Debt instrument		$ 4,684					$ 4,684		$ 4,732
Long-term Debt [Member] | 2015 Term Facility [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Payments on long-term debt		48	375
Debt instrument		$ 750					$ 750		$ 750
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
Proceeds from issuance of debt					$ 2,200
Minimum [Member] | Depositary Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued upon conversion		1.85014					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					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					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					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	2,043,780