INCOME TAXES - Effective Income Tax Rate Applicable to Continuing Operations (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
U.S. federal statutory income tax	$ 354	$ 112	$ 113
State income taxes, net of federal tax benefit	14	7	3
REIT income not subject to federal income tax	(161)	(101)	(94)
Foreign taxes	(2)	(8)	8
Provision for unrecognized tax benefits	(4)	(193)	(6)
Repatriation of Canadian earnings	0	21	0
State income tax settlement	0	0	(10)
Domestic production activities deduction	0	(13)	0
Other, net	(16)	4	(4)
Total income tax provision (benefit)	$ 185us-gaap_IncomeTaxExpenseBenefit	$ (171)us-gaap_IncomeTaxExpenseBenefit	$ 10us-gaap_IncomeTaxExpenseBenefit
Effective income tax rate	18.30%	(53.40%)	3.10%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for qualified production activity.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to increase (decrease) in income tax contingencies. Including, but not limited to, domestic tax contingency, foreign tax contingency, state and local tax contingency, and other contingencies.

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