Consolidated Balance Sheet (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Trade, allowance for doubtful accounts	$ 6	$ 7
Preferred stock, shares authorized	50,000,000us-gaap_PreferredStockSharesAuthorized	50,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, shares outstanding	0us-gaap_PreferredStockSharesOutstanding
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	450,000,000us-gaap_CommonStockSharesAuthorized	450,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares outstanding	166,070,057us-gaap_CommonStockSharesOutstanding	145,338,342us-gaap_CommonStockSharesOutstanding
Treasury stock, shares	1,588,990us-gaap_TreasuryStockShares	18,742,288us-gaap_TreasuryStockShares
Series A Preferred Stock [Member]
Preferred Stock, par value	$ 0.01	$ 0.01
Preferred stock, shares outstanding	0	0
Series B Preferred Stock [Member]
Preferred Stock, par value	$ 0.01	$ 0.01
Preferred stock, shares outstanding	0	3,803,774

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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