Consolidated Statements of Equity (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Stockholders' Equity [Abstract]
Preferred dividends related to noncontrolling interest	$ 13	$ 17	$ 16
Shares issued in excess of principal amounts related to converted securities		$ 28