Consolidated Statements of Operations (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]
REVENUE	$ 1,851.4	$ 1,756.2	$ 3,488.9	$ 3,299.2
OPERATING EXPENSES:
Salaries and related expenses	1,170.2	1,120.2	2,358.8	2,252.3
Office and general expenses	485.4	461.2	946.0	914.5
Total operating expenses	1,655.6	1,581.4	3,304.8	3,166.8
OPERATING INCOME	195.8	174.8	184.1	132.4
EXPENSES AND OTHER INCOME:
Interest expense	(22.6)	(37.5)	(42.8)	(74.3)
Interest income	6.6	5.8	12.8	12.2
Other (expense) income, net	(11.2)	4.8	(9.5)	6.6
Total (expenses) and other income	(27.2)	(26.9)	(39.5)	(55.5)
Income before income taxes	168.6	147.9	144.6	76.9
Provision for income taxes	65.3	62.0	63.6	49.6
Income of consolidated companies	103.3	85.9	81.0	27.3
Equity in net income of unconsolidated affiliates	0.4	0.2	0.3	0.3
NET INCOME	103.7	86.1	81.3	27.6
Net income attributable to noncontrolling interests	(4.3)	(3.3)	(2.8)	(1.1)
NET INCOME ATTRIBUTABLE TO IPG	99.4	82.8	78.5	26.5
Dividends on preferred stock	0	(2.9)	0	(5.8)
NET INCOME AVAILABLE TO IPG COMMON STOCKHOLDERS	$ 99.4	$ 79.9	$ 78.5	$ 20.7
Earnings per share available to IPG common stockholders - basic	$ 0.24	$ 0.19	$ 0.19	$ 0.05
Earnings per share available to IPG common stockholders - diluted	$ 0.23	$ 0.18	$ 0.18	$ 0.05
Weighted Average Number of Shares Outstanding, Basic	421.1	425.1	421.9	419.7
Weighted Average Number of Shares Outstanding, Diluted	428.1	448.3	428.5	425.1
Dividends declared per common share	$ 0.095	$ 0.075	$ 0.190	$ 0.150