Consolidated Statements of Total Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Comprehensive Income [Abstract]
Shareholders' comprehensive income (loss)	$ 457	$ 388	$ 1,389	$ 1,736
Net income (loss) attributable to redeemable noncontrolling interest	(1)	(2)	(2)	3
Net income (loss) attributable to other noncontrolling interest	(2)	(1)	(7)	(6)
Other comprehensive income (loss) attributable to redeemable noncontrolling interest	(9)	(6)	(21)	(6)
Other comprehensive income (loss) attributable to other noncontrolling interest	(1)	0	(1)	1
Total comprehensive income	$ 444	$ 379	$ 1,358	$ 1,728