Equity and Earnings Per Share - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended
Feb. 27, 2013	Mar. 05, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares of PHI common stock		17,922,077
Public offering price		$ 19.25
Underwriting discount		$ 0.67375
Initial pricing of equity forward instruments		$ 18.57625
Forward sale price	17.39
Proceeds from equity forward transaction	$ 312

Initial pricing of equity forward instruments.

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- Definition

Public offering price.

+ References

No definition available.

+ Details

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- Definition

Underwriting discount per share.

+ References

No definition available.

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- Definition

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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.29)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 30

-Article 5

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- Definition

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

+ References

No definition available.

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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

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