Share Repurchase Program (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Number of shares repurchased	14.9us-gaap_TreasuryStockSharesAcquired	31.8us-gaap_TreasuryStockSharesAcquired	32.7us-gaap_TreasuryStockSharesAcquired
Aggregated cost, including fees	$ 275.1	$ 481.8	$ 350.5
Average price per share, including fees	$ 18.41	$ 15.17	$ 10.72
2014 Share Repurchase Program
Share repurchase program, initial authorized amount	300.0
Remaining available for repurchase	143.6
2013 Share Repurchase Program
Share repurchase program, initial authorized amount		300.0
Share repurchase program, increased authorized amount		500.0
2012 Share Repurchase Program
Share repurchase program, initial authorized amount			300.0
Share repurchase program, increased authorized amount			$ 400.0

The remaining amount authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	ipg_ShareRepurchaseProgramRemainingAmountforRepurchase
Namespace Prefix:	ipg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount authorized by an entity's Board of Directors under a stock repurchase plan after program increase.

+ References

No definition available.

+ Details

Name:	ipg_StockRepurchaseProgramAuthorizedAmountAfterProgramIncrease
Namespace Prefix:	ipg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of stock repurchase plan authorized.

+ References

No definition available.

+ Details

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Total cost of shares repurchased divided by the total number of shares repurchased.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

+ Details

Name:	us-gaap_TreasuryStockAcquiredAverageCostPerShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares that have been repurchased during the period and are being held in treasury.

+ References

+ Details

Name:	us-gaap_TreasuryStockSharesAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

+ Details

Name:	us-gaap_TreasuryStockValueAcquiredCostMethod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=ipg_ShareRepurchaseProgramOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=ipg_ShareRepurchaseProgramThreeMemberDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=ipg_ShareRepurchaseProgramTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: