Stock-based Compensation - Summary of Activity for Non-voting Time-vested Restricted Stock Granted to Directors (Detail) (Non-Voting Time-Vested Restricted Stock Units [Member], USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share unit, Beginning Balance	61,258
Share unit, Granted	142,726
Share unit, Forfeited	0
Share unit, Vested and released to participants	(12,329)
Share unit, Ending Balance	191,655	61,258
Weighted Average Grant Fair Value, Beginning Balance	$ 24.11
Weighted Average Grants Date Fair Value, Granted	$ 43.25	$ 35.09
Weighted Average Grants Date Fair Value, Forfeited	$ 0
Weighted Average Grants Date Fair Value, Vested and released to participants	$ (21.05)
Weighted Average Grant Fair Value, Ending Balance	$ 38.56	$ 24.11
Remaining Average Contractual Life, Ending	2 years 3 months 4 days	1 year 7 months 24 days
Aggregate Value, Beginning Balance	$ 1,477
Aggregate Value, Ending Balance	7,391	1,477
Director [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Share unit, Beginning Balance	3,048
Share unit, Granted	2,202
Share unit, Forfeited	0
Share unit, Vested and released to participants	(762)
Share unit, Ending Balance	4,488	3,048
Weighted Average Grant Fair Value, Beginning Balance	$ 38.44
Weighted Average Grants Date Fair Value, Granted	$ 44.04
Weighted Average Grants Date Fair Value, Forfeited	$ 0
Weighted Average Grants Date Fair Value, Vested and released to participants	$ (38.44)
Weighted Average Grant Fair Value, Ending Balance	$ 41.19	$ 38.44
Remaining Average Contractual Life, Ending	2 years 5 months 23 days	2 years 10 months 6 days
Aggregate Value, Beginning Balance	117
Aggregate Value, Ending Balance	$ 185	$ 117

Stock-based Compensation - Summary of Activity for Non-voting Time-vested Restricted Stock Granted to Directors (Detail) (Non-Voting Time-Vested Restricted Stock Units [Member], USD $)
In Thousands, except Share data, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]

Share unit, Beginning Balance

61,258us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber

Share unit, Granted

142,726us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod

Share unit, Forfeited

0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod

Share unit, Vested and released to participants

(12,329)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod

Share unit, Ending Balance

191,655us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber

61,258us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber

Weighted Average Grant Fair Value, Beginning Balance

$ 24.11us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue

Weighted Average Grants Date Fair Value, Granted

$ 43.25us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue

$ 35.09us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue

Weighted Average Grants Date Fair Value, Forfeited

$ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue

Weighted Average Grants Date Fair Value, Vested and released to participants

$ (21.05)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue

Weighted Average Grant Fair Value, Ending Balance

$ 38.56us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue

$ 24.11us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue

Remaining Average Contractual Life, Ending

2 years 3 months 4 days

1 year 7 months 24 days

Aggregate Value, Beginning Balance

$ 1,477phii_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingAggregateValue

Aggregate Value, Ending Balance

7,391phii_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingAggregateValue

1,477phii_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingAggregateValue

Director [Member]

Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]

Share unit, Beginning Balance

3,048us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Share unit, Granted

2,202us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Share unit, Forfeited

0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Share unit, Vested and released to participants

(762)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Share unit, Ending Balance

4,488us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Weighted Average Grant Fair Value, Beginning Balance

$ 38.44us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Weighted Average Grants Date Fair Value, Granted

$ 44.04us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Weighted Average Grants Date Fair Value, Forfeited

$ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Weighted Average Grants Date Fair Value, Vested and released to participants

$ (38.44)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Weighted Average Grant Fair Value, Ending Balance

$ 41.19us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Remaining Average Contractual Life, Ending

2 years 5 months 23 days

2 years 10 months 6 days

Aggregate Value, Beginning Balance

117phii_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingAggregateValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

Aggregate Value, Ending Balance

$ 185phii_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingAggregateValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

$ 117phii_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingAggregateValue
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_DirectorMember
/ us-gaap_StatementClassOfStockAxis
= phii_NonVotingTimeVestedRestrictedStockUnitsMember

- Definition

Share based compensation arrangement by share based payment award equity instruments other than options outstanding aggregate value.

+ References

No definition available.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Period Type:	instant

- Definition

Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (e)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Period Type:	duration

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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