Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2014

Earnings Per Share [Abstract]

Earnings per share

				2014		2013		2012
Net earnings				$	458,343	$	407,197	$	391,240
Less: net earnings attributable to unvested restricted stock					(7,497)		(6,638)		(6,982)
		Net earnings available to common stock		$	450,846	$	400,559	$	384,258
Weighted-average common shares outstanding					97,591		98,853		100,176
Dilutive effect of outstanding securities (determined using treasury
	stock method)				260		260		280
		Weighted-average common shares and potential common
			shares outstanding		97,851		99,113		100,456
Earnings per common share
		Basic		$	4.62	$	4.05	$	3.84
		Diluted		$	4.61	$	4.04	$	3.83