Capital Stock (Tables)

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Capital Stock

	Common Shares in Treasury	Common Shares Outstanding
Balance at January 1, 2015	19,813,079	94,704,173
Shares tendered as payment for option rights exercised	14,542	(14,542	)
Shares issued for exercise of option rights		1,133,050
Shares tendered in connection with grants of restricted stock	111,433	(111,433	)
Net shares issued for grants of restricted stock		110,277
Treasury stock purchased	3,575,000	(3,575,000	)
Balance at December 31, 2015	23,514,054	92,246,525
Shares tendered as payment for option rights exercised	3,441	(3,441	)
Shares issued for exercise of option rights		733,876
Shares tendered in connection with grants of restricted stock	59,916	(59,916	)
Net shares issued for grants of restricted stock		95,987
Balance at December 31, 2016	23,577,411	93,013,031
Shares tendered as payment for option rights exercised	16,545	(16,545	)
Shares issued for exercise of option rights		1,152,015
Shares tendered in connection with grants of restricted stock	82,777	(82,777	)
Net shares issued for grants of restricted stock		(182,079	)
Balance at December 31, 2017	23,676,733	93,883,645