Stockholders' Equity and Earnings Per Common Share (Tables)

12 Months Ended

Dec. 31, 2017

Stockholders' Equity and Earnings Per Common Share [Abstract]

Schedule of Basic and Diluted Earnings Per Share

Net income per common share is determined as follows:

	Year Ended December 31
	2017		2016		2015
	(in millions of dollars, except share data)
Numerator
Net Income	$	994.2	$	931.4	$	867.1
Denominator (000s)
Weighted Average Common Shares - Basic	226,492.4		235,445.7		246,986.7
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	842.8		533.5		868.0
Weighted Average Common Shares - Assuming Dilution	227,335.2		235,979.2		247,854.7
Net Income Per Common Share
Basic	$	4.39	$	3.96	$	3.51
Assuming Dilution	$	4.37	$	3.95	$	3.50

Treasury Stock Transactions

Our board of directors has authorized the repurchase of Unum Group's common stock under the following repurchase programs:

	Share Repurchase Program Authorized During
	May 2017		May 2016		May 2015
	(in millions of dollars)
Authorized Repurchase Amount	$	750.0	$	750.0	$	750.0
Remaining Repurchase Amount at Year End 2017	$	512.8	$	—	$	—

The May 2017 share repurchase program has an expiration date of November 25, 2018.

Common stock repurchases, which are accounted for using the cost method and classified as treasury stock until otherwise retired, were as follows:

	Year Ended December 31
	2017		2016		2015
	(in millions)
Shares Repurchased	8.2		11.9		12.3
Cost of Shares Repurchased (1)	$	400.4	$	403.3	$	426.7

(1) Includes commissions of $0.3 million, $0.2 million, and $0.3 million for the years ended December 31, 2017, 2016, and 2015, respectively.