Consolidated Statement of Stockholders Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock [Member]	Additional Paid In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Adoption of ASU No. 2016-09 (Note 2) | Accounting Standards Update 2016-09 [Member]	$ 8	$ 0	$ 8	$ 0	$ 0
BALANCE at Jan. 1, 2017	7,631	$ 0	6,791	884	$ (44)
BALANCE, Shares at Dec. 31, 2016		146,489			430
BALANCE at Dec. 31, 2016	7,623	$ 0	6,783	884	$ (44)
Net income (loss)	802	$ 0	0	802	$ 0
Common stock issued in business combination (Shares)		2,177			0
Common stock issued in business combination	291	$ 0	291	0	$ 0
Stock options exercised	0	$ 0	0	0	$ 0
Stock options exercised, shares		20			0
Grants of restricted stock, shares		439			0
Performance unit share conversion, shares		249			0
Cancellation of restricted stock, shares		(59)			0
Stock-based compensation	26	$ 0	26	0	$ 0
Purchase of treasury stock	(21)	$ 0	0	0	$ (21)
Purchase of treasury stock, shares		0			162
BALANCE, Shares at Jun. 30, 2017		149,315			592
BALANCE at Jun. 30, 2017	$ 8,729	$ 0	$ 7,108	$ 1,686	$ (65)