Capital Stock (Tables)

12 Months Ended

Dec. 31, 2017

Capital Stock [Abstract]

Summary of Common Share Activity

A summary of common share activity for the years ended December 31 follows (in shares):

	2017		2016		2015
Common shares outstanding at January 1	139,840,228		139,441,298		139,000,471
Shares repurchased	(6,157,010	)	(162,563	)	(165,138	)
Shares issued upon exercise of employee stock options	299,050		348,640		207,890
Restricted stock issued to employees, net of forfeitures	269,025		187,209		375,575
Shares issued to non-employee directors	24,316		25,644		22,500
Common shares outstanding at December 31	134,275,609		139,840,228		139,441,298