Equity And Earnings Per Share (Narrative) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Feb. 27, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Public offering price	$ 19.25
Shares of PHI common stock	17,922,077
Underwriting discount	$ 0.67375
Initial pricing of equity forward instruments	$ 18.57625
Forward sale price		17.39
Proceeds from equity forward transaction	$ 312
Weighted-average price of shares	$ 19.93
Number of Shares	102,933
Value of stock outstanding	$ 2

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Underwriting Discount Per Share

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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The forward price on the price risk forward or futures contract, such as a gas futures contract.

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The cash inflow from the issuance of common stock, preferred stock, treasury stock, stock options, and other types of equity.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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The amount allocated to treasury stock. Treasury stock is common and preferred shares of an entity that were issued, repurchased by the entity, and are held in its treasury.

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