CONSOLIDATED STATEMENTS OF EQUITY (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Statement of Stockholders' Equity [Abstract]
Increase to paid-in capital for change in ownership interest upon equity issuance	$ 130	$ 194
Net income (loss) attributable to common stockholders, including increase to paid-in capital for change in ownership interest upon equity issuance	2,521	(2,455)
Paid-in Capital [Member]
Statement [Line Items]
Conversion of subordinated limited partner units to common units, tax		92
Noncontrolling Interests [Member]
Statement [Line Items]
Conversion of subordinated limited partner units to common units, tax		$ (92)