Net Income Per Common Share (Tables)

9 Months Ended

Sep. 30, 2015

Earnings Per Share [Abstract]

Computation of net income per common share

(Thousands of dollars except per share data)	Three Months Ended September 30,						Nine Months Ended September 30,
	2015			2014			2015			2014
Basic
Average common shares outstanding	92,196,458			94,800,191			92,398,962			96,744,423
Net income	$	374,491		$	326,240		$	855,832		$	733,144
Less net income allocated to unvested restricted shares	(1,669		)	(1,992		)	(3,683		)	(4,237		)
Net income allocated to common shares	$	372,822		$	324,248		$	852,149		$	728,907
Basic net income per common share	$	4.04		$	3.42		$	9.22		$	7.53
Diluted
Average common shares outstanding	92,196,458			94,800,191			92,398,962			96,744,423
Stock options and other contingently issuable shares (1)	1,698,414			1,913,852			1,864,371			1,926,576
Average common shares outstanding assuming dilution	93,894,872			96,714,043			94,263,333			98,670,999
Net income	$	374,491		$	326,240		$	855,832		$	733,144
Less net income allocated to unvested restricted shares
assuming dilution	(1,641		)	(1,955		)	(3,618		)	(4,160		)
Net income allocated to common shares assuming
dilution	$	372,850		$	324,285		$	852,214		$	728,984
Diluted net income per common share	$	3.97		$	3.35		$	9.04		$	7.39

⁽¹⁾  Stock options and other contingently issuable shares excluded 34,473 and 31,615 shares due to their anti-dilutive effect for the three and nine months ended September 30, 2015. Stock options and other contingently issuable shares excluded 15,885 shares for the nine months ended September 30, 2014.There were no options excluded due to their anti-dilutive effect for the three months ended September 30, 2014.