Note 16 - Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

2014 Quarters (In thousands, except per share amounts)	First		Second		Third		Fourth
Operating revenue	$	159,409	$	168,423	$	171,550	$	173,547
Operating income		8,640		12,932		13,042		16,392
Net income		5,287		7,926		7,652		8,969
Basic earnings per common share		0.16		0.24		0.23		0.27
Diluted earnings per common share		0.16		0.24		0.23		0.27

2013 Quarters (In thousands, except per share amounts)	First		Second		Third		Fourth
Operating revenue	$	164,474	$	161,413	$	167,103	$	166,224
Operating income		12,538		13,121		13,653		12,683
Net income		7,202		7,667		7,977		7,301
Basic earnings per common share		0.22		0.23		0.24		0.22
Diluted earnings per common share		0.22		0.23		0.24		0.22