Accumulated Other Comprehensive Income (Tables)

9 Months Ended

Sep. 30, 2015

Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

The following tables present changes in the accumulated balances for each component of other comprehensive income attributable to CME Group, including current period other comprehensive income and reclassifications out of accumulated other comprehensive income:

(in millions)	Investment Securities			Defined Benefit Plans			Derivative Investments			Foreign Currency Translation			Total
Balance at December 31, 2014	$	(22.9	)	$	(31.3	)	$	62.6		$	(2.2	)	$	6.2
Other comprehensive income before reclassifications and income tax benefit (expense)	(91.0		)	(0.3		)	(4.7		)	(10.0		)	(106.0		)
Amounts reclassified from accumulated other comprehensive income	(3.4		)	2.0			0.9			—			(0.5		)
Income tax benefit (expense)	1.2			(0.6		)	1.5			3.6			5.7
Net current period other comprehensive income attributable to CME Group	(93.2		)	1.1			(2.3		)	(6.4		)	(100.8		)
Balance at September 30, 2015	$	(116.1	)	$	(30.2	)	$	60.3		$	(8.6	)	$	(94.6	)

(in millions)	Investment Securities			Defined Benefit Plans			Derivative Investments			Foreign Currency Translation			Total
Balance at December 31, 2013	$	98.9		$	(12.8	)	$	65.0		$	0.9		$	152.0
Other comprehensive income before reclassifications and income tax benefit (expense)	(10.7		)	(3.2		)	(1.1		)	(2.7		)	(17.7		)
Amounts reclassified from accumulated other comprehensive income	—			0.2			—			—			0.2
Income tax benefit (expense)	(6.5		)	1.1			0.4			1.0			(4.0		)
Net current period other comprehensive income attributable to CME Group	(17.2		)	(1.9		)	(0.7		)	(1.7		)	(21.5		)
Balance at September 30, 2014	$	81.7		$	(14.7	)	$	64.3		$	(0.8	)	$	130.5