Summarized Quarterly Financial Data (unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

Summarized Quarterly Financial Data—(in millions, except per share amounts)

	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Year ended December 31, 2017:
Revenues	$	1,211		$	1,241		$	1,403		$	1,746
Income from operations	376			274			297			441
Net income	172			21			90			280
Net income (loss) attributable to common stockholders	54			(285		)	(289		)	127
Net income (loss) per share attributable to common stockholders—basic and diluted (1)	0.23			(1.23		)	(1.24		)	0.54
Year ended December 31, 2016:
Revenues	$	69		$	177		$	465		$	572
Income (loss) from operations	(91		)	(76		)	15			122
Net income (loss)	(349		)	(335		)	(131		)	150
Net income (loss) attributable to common stockholders	(321		)	(298		)	(101		)	110
Net income (loss) per share attributable to common stockholders—basic and diluted (1)	(1.41		)	(1.31		)	(0.44		)	0.48

(1) The sum of the quarterly net income (loss) per share—basic and diluted may not equal the full year amount as the computations of the weighted average common shares outstanding for basic and diluted shares outstanding for each quarter and the full year are performed independently.