Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended										6 Months Ended	12 Months Ended
		Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Mar. 31, 2013	Jul. 10, 2013	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2013
Quarterly Financial Data [Line Items]
Revenues		$ 8,071	$ 8,107	$ 7,975	$ 8,027	$ 8,292	$ 8,973	$ 8,488	$ 8,789
Operating income (loss)		8	(197)	(2)	501	318	(2,540)	(192)	519
Net loss		$ (554)	$ (836)	$ (585)	$ (20)	$ (224)	$ (2,379)	$ (765)	$ 23
Basic and diluted net loss per common share	[1]	$ (0.14)	$ (0.21)	$ (0.15)	$ (0.01)	$ (0.06)	$ (0.60)	$ (0.19)	$ 0.01
Successor [Member]
Quarterly Financial Data [Line Items]
Revenues										$ 8,875	$ 0		$ 32,180	$ 34,532	$ 16,891
Operating income (loss)										420	(14)		310	(1,895)	(970)
Net loss										$ (151)	(9)		$ (1,995)	$ (3,345)	$ (1,860)
Basic and diluted net loss per common share										$ (0.04)			$ (0.50)	$ (0.85)	$ (0.54)
Predecessor [Member]
Quarterly Financial Data [Line Items]
Revenues											8,793	$ 18,602
Operating income (loss)											29	(885)
Net loss											$ (643)	$ (1,158)
Basic and diluted net loss per common share											$ (0.21)	$ (0.38)

[1] (1)The sum of the quarterly earnings per share amounts may not equal the annual amounts because of the changes in the weighted average number of shares outstanding during the year.