Common Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2015

Equity [Abstract]

Weighted Average Number of Common Shares Used In the Computation of Basic and Diluted Earnings per Share

The weighted average number of shares used in the computation of net income per share was as follows:

	2015	2014	2013
Basic	124,040,313	127,873,708	135,304,752
Diluted	130,188,866	133,651,855	140,742,922

Schedule of Changes in Shares of Common Stock Outstanding

Changes in shares of common stock outstanding, net of treasury shares, are presented below. Shares of common stock issued and outstanding do not include shares related to unissued restricted stock units and unexercised stock options.

	2015		2014		2013
Balance, beginning of year	126,748,836		132,233,167		136,017,732
Shares issued	1,061,026		332,137		139,790
Shares repurchased	(4,502,025	)	(5,816,468	)	(3,924,355)
Balance, end of year	123,307,837		126,748,836		132,233,167