Net Income Per Common Share

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

NET INCOME PER COMMON SHARE

NET INCOME PER COMMON SHARE

Basic and diluted earnings per share are calculated using the treasury stock method.

(Thousands of dollars except per share data)	Three Months Ended March 31,
	2018		2017
Basic
Average common shares outstanding	93,339,564		92,550,559
Net income	$	250,127	$	239,152
Basic net income per common share	$	2.68	$	2.58
Diluted
Average common shares outstanding	93,339,564		92,550,559
Stock options and other contingently issuable shares (1)	2,138,874		1,931,574
Non-vested restricted stock grants	67,714		59,726
Average common shares outstanding assuming dilution	95,546,152		94,541,859
Net income	$	250,127	$	239,152
Diluted net income per common share	$	2.62	$	2.53

⁽¹⁾  Stock options and other contingently issuable shares for the three months endedMarch 31, 2017 excludes 40,074 shares due to their anti-dilutive effect.There werenostock options and other contingently issuable shares excludeddue to their anti-dilutive effect for the three months endedMarch 31, 2018.