Revenue (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Condensed Income Statement [Table Text Block]

CONSOLIDATED STATEMENT OF OPERATIONS

	Year ended December 31, 2017									Year ended December 31, 2016
	As Revised 1			ASC 606 Adjustments			As Adjusted			As Revised 1			ASC 606 Adjustments			As Adjusted
REVENUE:
Net revenue	$	7,508.7		$	(35.2	)	$	7,473.5		$	7,456.9		$	(4.6	)	$	7,452.3
Billable expenses	373.7			1,200.4			1,574.1			389.7			1,214.2			1,603.9
Total revenue	7,882.4			1,165.2			9,047.6			7,846.6			1,209.6			9,056.2
OPERATING EXPENSES:
Salaries and related expenses	4,990.7			—			4,990.7			4,942.2			—			4,942.2
Office and other direct expenses	1,268.8			—			1,268.8			1,274.9			—			1,274.9
Billable expenses	373.7			1,200.4			1,574.1			389.7			1,214.2			1,603.9
Cost of services	6,633.2			1,200.4			7,833.6			6,606.8			1,214.2			7,821.0
Selling, general and administrative expenses	118.5			—			118.5			138.6			—			138.6
Depreciation and amortization	157.1			—			157.1			160.2			—			160.2
Total operating expenses	6,908.8			1,200.4			8,109.2			6,905.6			1,214.2			8,119.8
OPERATING INCOME	973.6			(35.2		)	938.4			941.0			(4.6		)	936.4
EXPENSES AND OTHER INCOME:
Interest expense	(90.8		)	—			(90.8		)	(90.6		)	—			(90.6		)
Interest income	19.4			—			19.4			20.1			—			20.1
Other expense, net	(26.2		)	—			(26.2		)	(40.3		)	—			(40.3		)
Total (expenses) and other income	(97.6		)	—			(97.6		)	(110.8		)	—			(110.8		)
Income before income taxes	876.0			(35.2		)	840.8			830.2			(4.6		)	825.6
Provision for income taxes	281.9			(10.6		)	271.3			198.0			(1.1		)	196.9
Income of consolidated companies	594.1			(24.6		)	569.5			632.2			(3.5		)	628.7
Equity in net income of unconsolidated affiliates	0.9			—			0.9			0.3			—			0.3
NET INCOME	595.0			(24.6		)	570.4			632.5			(3.5		)	629.0
Net income attributable to noncontrolling interests	(16.0		)	—			(16.0		)	(24.0		)	—			(24.0		)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$	579.0		$	(24.6	)	$	554.4		$	608.5		$	(3.5	)	$	605.0
Earnings per share available to IPG common stockholders:
Basic	$	1.49		$	(0.07	)	$	1.42		$	1.53		$	(0.01	)	$	1.52
Diluted	$	1.46		$	(0.06	)	$	1.40		$	1.49		$	(0.01	)	$	1.48
Weighted-average number of common shares outstanding:
Basic	389.6			—			389.6			397.9			—			397.9
Diluted	397.3			—			397.3			408.0			—			408.0

1 These amounts have been revised for the new presentation as described in Note 1.

Condensed Cash Flow Statement [Table Text Block]

CONSOLIDATED STATEMENT OF CASH FLOWS

	Year ended December 31, 2017
	As Reported			ASC 606 Adjustments			As Adjusted
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$	595.0		$	(24.6	)	$	570.4
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	157.1			—			157.1
Provision for uncollectible receivables	9.5			—			9.5
Amortization of restricted stock and other non-cash compensation	82.0			—			82.0
Net amortization of bond discounts and deferred financing costs	5.8			—			5.8
Deferred income tax provision	1.1			(10.6		)	(9.5		)
Net losses on sales of businesses	24.1			—			24.1
Other	12.7			—			12.7
Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash:
Accounts receivable	37.6			—			37.6
Expenditures billable to clients	(165.5		)	165.5			—
Accounts receivable, billable to clients	—			(165.5		)	(165.5		)
Other current assets	27.4			22.7			50.1
Accounts payable	311.9			24.5			336.4
Accrued liabilities	(241.3		)	—			(241.3		)
Contract liabilities	—			(12.0		)	(12.0		)
Other non-current assets and liabilities	24.4			—			24.4
Net cash provided by operating activities	881.8			—			881.8
CASH FLOWS FROM INVESTING ACTIVITIES:
Net cash used in investing activities	(196.2		)	—			(196.2		)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net cash used in financing activities	(1,004.9		)	—			(1,004.9		)
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash	16.8			—			16.8
Net decrease in cash, cash equivalents and restricted cash	(302.5		)	—			(302.5		)
Cash, cash equivalents and restricted cash at beginning of period	1,100.2			—			1,100.2
Cash, cash equivalents and restricted cash at end of period	$	797.7		$	—		$	797.7

	Year ended December 31, 2016
	As Reported			ASC 606 Adjustments			As Adjusted
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$	632.5		$	(3.5	)	$	629.0
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	160.2			—			160.2
Provision for uncollectible receivables	16.7			—			16.7
Amortization of restricted stock and other non-cash compensation	85.6			—			85.6
Net amortization of bond discounts and deferred financing costs	5.6			—			5.6
Deferred income tax provision	45.7			(1.1		)	44.6
Net losses on sales of businesses	41.4			—			41.4
Other	35.5			—			35.5
Changes in assets and liabilities, net of acquisitions and divestitures, providing (using) cash:
Accounts receivable	(220.7		)	—			(220.7		)
Expenditures billable to clients	(2.2		)	2.2			—
Accounts receivable, billable to clients	—			(2.2		)	(2.2		)
Other current assets	(4.8		)	5.3			0.5
Accounts payable	(126.1		)	(21.3		)	(147.4		)
Accrued liabilities	(61.1		)	—			(61.1		)
Contract liabilities	—			20.6			20.6
Other non-current assets and liabilities	(95.5		)	—			(95.5		)
Net cash provided by operating activities	512.8			—			512.8
CASH FLOWS FROM INVESTING ACTIVITIES:
Net cash used in investing activities	(263.9		)	—			(263.9		)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net cash used in financing activities	(666.4		)	—			(666.4		)
Effect of foreign exchange rate changes on cash, cash equivalents and restricted cash	11.6			—			11.6
Net decrease in cash, cash equivalents and restricted cash	(405.9		)	—			(405.9		)
Cash, cash equivalents and restricted cash at beginning of period	1,506.1			—			1,506.1
Cash, cash equivalents and restricted cash at end of period	$	1,100.2		$	—		$	1,100.2

Condensed Balance Sheet [Table Text Block]

CONSOLIDATED BALANCE SHEET

	December 31, 2017
	As Reported			ASC 606 Adjustments			As Adjusted
ASSETS:
Cash and cash equivalents	$	790.9		$	—		$	790.9
Accounts receivable, net of allowance of $42.7	4,585.0			—			4,585.0
Expenditures billable to clients	1,747.4			(1,747.4		)	—
Accounts receivable, billable to clients	—			1,747.4			1,747.4
Assets held for sale	5.7			—			5.7
Other current assets	335.1			11.4			346.5
Total current assets	7,464.1			11.4			7,475.5
Property and equipment, net of accumulated depreciation of $1,036.2	650.4			—			650.4
Deferred income taxes	236.0			(2.0		)	234.0
Goodwill	3,820.4			—			3,820.4
Other intangible assets	140.7			—			140.7
Other non-current assets	383.6			0.1			383.7
TOTAL ASSETS	$	12,695.2		$	9.5		$	12,704.7
LIABILITIES:
Accounts payable	$	6,907.8		$	(487.6	)	$	6,420.2
Accrued liabilities	674.7			—			674.7
Contract liabilities	—			484.7			484.7
Short-term borrowings	84.9			—			84.9
Current portion of long-term debt	2.0			—			2.0
Liabilities held for sale	8.8			—			8.8
Total current liabilities	7,678.2			(2.9		)	7,675.3
Long-term debt	1,285.6			—			1,285.6
Deferred compensation	476.6			—			476.6
Other non-current liabilities	766.9			1.9			768.8
TOTAL LIABILITIES	10,207.3			(1.0		)	10,206.3
Redeemable noncontrolling interests	252.1			—			252.1
STOCKHOLDERS’ EQUITY:
Common stock	38.6			—			38.6
Additional paid-in capital	955.2			—			955.2
Retained earnings	2,093.6			10.9			2,104.5
Accumulated other comprehensive loss, net of tax	(827.4		)	(0.4		)	(827.8		)
	2,260.0			10.5			2,270.5
Less: Treasury stock	(59.0		)	—			(59.0		)
Total IPG stockholders’ equity	2,201.0			10.5			2,211.5
Noncontrolling interests	34.8			—			34.8
TOTAL STOCKHOLDERS’ EQUITY	2,235.8			10.5			2,246.3
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$	12,695.2		$	9.5		$	12,704.7

Revenue from External Customers by Geographic Areas [Table Text Block]

	Years ended December 31,
Total revenue:	2018		2017		2016
United States	$	5,851.0	$	5,417.3	$	5,452.6
International:
United Kingdom	881.4		775.7		788.8
Continental Europe	840.2		780.6		764.1
Asia Pacific	1,170.8		1,106.4		1,076.0
Latin America	389.0		386.6		417.2
Other	582.0		581.0		557.5
Total International	3,863.4		3,630.3		3,603.6
Total Consolidated	$	9,714.4	$	9,047.6	$	9,056.2

	Years ended December 31,
Net revenue:	2018		2017		2016
United States	$	4,825.0	$	4,458.8	$	4,443.2
International:
United Kingdom	711.7		613.1		604.3
Continental Europe	737.5		687.8		682.0
Asia Pacific	896.8		866.9		887.7
Latin America	350.1		350.8		367.8
Other	510.5		496.1		467.3
Total International	3,206.6		3,014.7		3,009.1
Total Consolidated	$	8,031.6	$	7,473.5	$	7,452.3

IAN	Years ended December 31,
Total revenue:	2018		2017		2016
United States	$	4,279.4	$	4,062.3	$	4,075.9
International	3,095.0		2,947.3		2,916.9
Total IAN	$	7,374.4	$	7,009.6	$	6,992.8
Net revenue:
United States	$	3,832.7	$	3,660.6	$	3,600.3
International	2,753.1		2,606.1		2,601.1
Total IAN	$	6,585.8	$	6,266.7	$	6,201.4

CMG	Years ended December 31,
Total revenue:	2018		2017		2016
United States	$	1,404.0	$	1,355.0	$	1,376.7
International	754.3		683.0		686.7
Total CMG	$	2,158.3	$	2,038.0	$	2,063.4
Net revenue:
United States	$	824.6	$	798.2	$	842.9
International	439.5		408.6		408.0
Total CMG	$	1,264.1	$	1,206.8	$	1,250.9

Contract with Customer, Asset and Liability [Table Text Block]

Contract Balances

The following table provides information about receivables, contract assets and contract liabilities from contracts with customers.

	December 31, 2018		December 31, 2017
Accounts receivable, net of allowance of $42.5 and $42.7, respectively	$	5,126.6	$	4,585.0
Accounts receivable, billable to clients	1,900.6		1,747.4
Contract assets	67.9		11.5
Contract liabilities (deferred revenue)	533.9		484.7