Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
REVENUE	$ 1,841.1	$ 1,700.4	$ 5,330.0	$ 4,999.6
OPERATING EXPENSES:
Salaries and related expenses	1,195.2	1,093.6	3,554.0	3,345.9
Office and general expenses	474.6	465.3	1,420.6	1,379.8
Total operating expenses	1,669.8	1,558.9	4,974.6	4,725.7
OPERATING INCOME	171.3	141.5	355.4	273.9
EXPENSES AND OTHER INCOME:
Interest expense	(20.7)	(23.7)	(63.5)	(98.0)
Interest income	7.5	5.8	20.3	18.0
Other expense, net	(0.6)	(46.6)	(10.1)	(40.0)
Total (expenses) and other income	(13.8)	(64.5)	(53.3)	(120.0)
Income before income taxes	157.5	77.0	302.1	153.9
Provision for income taxes	65.0	28.4	128.6	78.0
Income of consolidated companies	92.5	48.6	173.5	75.9
Equity in net income of unconsolidated affiliates	0.3	0.6	0.6	0.9
NET INCOME	92.8	49.2	174.1	76.8
Net income attributable to noncontrolling interests	(3.1)	(0.9)	(5.9)	(2.0)
NET INCOME ATTRIBUTABLE TO IPG	89.7	48.3	168.2	74.8
Dividends on preferred stock	0	(2.9)	0	(8.7)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 89.7	$ 45.4	$ 168.2	$ 66.1
Earnings per share available to IPG common stockholders - basic	$ 0.21	$ 0.11	$ 0.40	$ 0.16
Earnings per share available to IPG common stockholders - diluted	$ 0.21	$ 0.11	$ 0.39	$ 0.16
Weighted Average Number of Shares Outstanding, Basic	419.2	419.7	421.0	419.7
Weighted Average Number of Shares Outstanding, Diluted	426.4	426.1	427.2	424.8
Dividends declared per common share	$ 0.095	$ 0.075	$ 0.285	$ 0.225