Redeemable Preferred Stock (Details) $ / shares in Millions, $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended
	Jun. 30, 2016 USD ($)	Nov. 30, 2010 quarter director	Jun. 30, 2005	Dec. 31, 2010 USD ($) shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Series C Preferred Stock [Member]
Class of Stock [Line Items]
Number of shares of stock issued (shares) | shares				1,000
Percentage dividend rate on preferred stock				8.625%
Cash purchase price of Series C Preferred Stock				$ 1,000
Redemption value per share (usd per share) | $ / shares					$ 1
Liquidation value per share (usd per share) | $ / shares					$ 1
Preferred Stock, Voting Rights, Board of Directors, Election of Additional Members | director		2
Preferred Stock, Voting Rights, Board of Directors, Election of Additional Members, Number of Unpaid Dividend Quarters Trigger | quarter		6
Authorization and creation of any class of stock must be approved by the holders of Series C Preferred Stock		66.66%
Dividend paid on preferred stock					$ 86	$ 86	$ 86
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Percentage dividend rate on preferred stock	6.36%
Authorization and creation of any class of stock must be approved by the holders of Series C Preferred Stock			66.66%
Amount paid for redemption	$ 575
Dividend paid on preferred stock					$ 20	$ 37	$ 37