Note 11 - Quarterly Financial Information (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2012

Dec. 31, 2011

Schedule of Quarterly Financial Information [Table Text Block]

	Quarter
	First		Second		Third		Fourth
2012:
Operating revenues	$	1,165,922	$	1,255,130	$	1,295,792	$	1,338,136
Operating income	$	116,597	$	137,215	$	133,052	$	143,335
Net earnings	$	67,684	$	80,451	$	78,241	$	83,977
Basic earnings per share	$	0.58	$	0.69	$	0.66	$	0.71
Diluted earnings per share	$	0.57	$	0.67	$	0.65	$	0.70

2011:
Operating revenues	$	1,000,780	$	1,149,855	$	1,171,270	$	1,204,937
Operating income	$	89,823	$	113,443	$	118,680	$	122,287
Net earnings	$	50,095	$	65,696	$	68,650	$	72,565
Basic earnings per share	$	0.41	$	0.55	$	0.58	$	0.62
Diluted earnings per share	$	0.40	$	0.53	$	0.57	$	0.61