Consolidated Statements of Total Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement Of Comprehensive Income [Abstract]
Shareholders' comprehensive income (loss)	$ 397	$ 733	$ 932	$ 1,348
Net income (loss) attributable to redeemable noncontrolling interest	(1)	2	(1)	5
Net income (loss) attributable to other noncontrolling interest	(3)	(3)	(5)	(5)
Other comprehensive income (loss) attributable to redeemable noncontrolling interest	(3)	3	(12)	0
Other comprehensive income (loss) attributable to other noncontrolling interest	0	0	0	1
Total comprehensive income	$ 390	$ 735	$ 914	$ 1,349