Stockholders' Equity, Components of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive income (loss), beginning of period			$ (1,026)	$ 96
Other comprehensive income (loss) before reclassifications			(222)	(613)
Amounts reclassified from accumulated other comprehensive income (loss)			(133)	7
Total other comprehensive loss	$ (74)	$ (553)	(355)	(606)
Accumulated other comprehensive income (loss), end of period	(1,381)	(510)	(1,381)	(510)
Financial derivatives [Member]
Accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive income (loss), beginning of period			(80)	0
Other comprehensive income (loss) before reclassifications			185	(13)
Amounts reclassified from accumulated other comprehensive income (loss)			(148)	0
Total other comprehensive loss			37	(13)
Accumulated other comprehensive income (loss), end of period	(43)	(13)	(43)	(13)
Net unrealized holding gains on investments net of tax [Member]
Accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive income (loss), beginning of period			0	0
Other comprehensive income (loss) before reclassifications			(1)	1
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Total other comprehensive loss			(1)	1
Accumulated other comprehensive income (loss), end of period	(1)	1	(1)	1
Defined pension and other postretirement benefit plans [Member]
Accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive income (loss), beginning of period			(449)	(140)
Other comprehensive income (loss) before reclassifications			0	(7)
Amounts reclassified from accumulated other comprehensive income (loss)			15	7
Total other comprehensive loss			15	0
Accumulated other comprehensive income (loss), end of period	(434)	(140)	(434)	(140)
Foreign currency translation adjustments [Member]
Accumulated other comprehensive income (loss) [Line Items]
Accumulated other comprehensive income (loss), beginning of period			(497)	236
Other comprehensive income (loss) before reclassifications			(406)	(594)
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Total other comprehensive loss			(406)	(594)
Accumulated other comprehensive income (loss), end of period	$ (903)	$ (358)	$ (903)	$ (358)