Note 12 - Quarterly Financial Information (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2015

Notes Tables

Schedule of Quarterly Financial Information [Table Text Block]

	Quarter
	First		Second		Third		Fourth
2015:
Operating revenues	$	1,440,180	$	1,539,957	$	1,586,494	$	1,621,015
Operating income	$	155,220	$	173,735	$	193,846	$	192,893
Net earnings	$	91,932	$	103,419	$	115,139	$	116,746
Basic earnings per share	$	0.79	$	0.89	$	1.00	$	1.02
Diluted earnings per share	$	0.78	$	0.88	$	0.99	$	1.01
2014:
Operating revenues	$	1,406,908	$	1,547,867	$	1,601,156	$	1,609,511
Operating income	$	117,307	$	159,230	$	172,100	$	182,905
Net earnings	$	68,664	$	93,408	$	102,414	$	110,306
Basic earnings per share	$	0.59	$	0.80	$	0.87	$	0.94
Diluted earnings per share	$	0.58	$	0.79	$	0.87	$	0.93