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CONSOLIDATED STATEMENT OF STOCKHOLDERS’ EQUITY - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU \| Topic 606	$ 6				$ 6
Adoption of ASU \| ASU 2018-02	$ 0			$ (1)	1
Beginning Balance (in shares) at Dec. 31, 2017	59	60
Beginning Balance at Dec. 31, 2017	$ 1,337	$ 0	$ 1,044	(5)	298
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	309				309
Partial termination of 1.125% Warrants	(113)		(113)
1.625% Convertible Notes exchange transaction (in shares)		2
1.625% Convertible Notes exchange transaction	108		108
Other comprehensive loss, net	(5)			(5)
Share-based compensation	16		16
Ending Balance (in shares) at Jun. 30, 2018		62
Ending Balance at Jun. 30, 2018	$ 1,658	$ 0	1,055	(11)	614
Beginning Balance (in shares) at Mar. 31, 2018	61
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 202
Other comprehensive loss, net	2
Ending Balance (in shares) at Jun. 30, 2018		62
Ending Balance at Jun. 30, 2018	$ 1,658	$ 0	$ 1,055	$ (11)	$ 614