Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Basic and diluted earnings per share

	Years ended December 31,
	2014			2013			2012
	(millions, except per share data)
Net income (loss) attributable to Willis Group Holdings	$	362		$	365		$	(446	)
Basic weighted average number of shares outstanding	178			176			173
Dilutive effect of potentially issuable shares	3			3			—
Diluted weighted average number of shares outstanding	181			179			173
Basic earnings per share:
Net income (loss) attributable to Willis Group Holdings shareholders	$	2.03		$	2.07		$	(2.58	)
Dilutive effect of potentially issuable shares	(0.03		)	(0.03		)	—
Diluted earnings per share:
Net income (loss) attributable to Willis Group Holdings shareholders	$	2.00		$	2.04		$	(2.58	)