Redeemable Preferred Stock (Details)	1 Months Ended		3 Months Ended	12 Months Ended
	Nov. 30, 2010 director quarter	Jun. 30, 2005 director quarter shares	Dec. 31, 2010 USD ($) shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
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 | $			$ 1,000,000,000
Redemption value per share (usd per share)				$ 1,000,000
Liquidation value per share (usd per share)				$ 1,000,000
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 | $				$ 86,000,000	$ 86,000,000	$ 86,000,000
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Number of shares of stock issued (shares) | shares		575,000
Percentage dividend rate on preferred stock		6.36%
Redemption value per share (usd per share)				$ 1,000
Liquidation value per share (usd per share)				$ 1,000
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 | $				$ 37,000,000	$ 37,000,000	$ 37,000,000