Quarterly Financial Information (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2014

Quarterly Financial Information (Unaudited) [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

	First		Second		Third		Fourth
	(In Thousands, Except Per Share Data)
Year ended December 31, 2014
Operating revenue	$	224,481	$	226,785	$	217,092	$	202,997
Operating income	20,688		40,642		36,290		34,247
Income before income taxes	20,569		40,616		36,214		34,216
Net income	14,079		26,472		22,737		21,544
Net income per share, basic	0.16		0.30		0.26		0.25
Net income per share, diluted	0.16		0.30		0.26		0.25
Year ended December 31, 2013(1)
Operating revenue	$	134,273	$	133,992	$	130,645	$	183,348
Operating income	30,207		29,375		26,000		26,720
Income before income taxes	30,330		29,504		26,126		26,596
Net income	19,734		19,138		15,868		15,842
Net income per share, basic	0.23		0.23		0.19		0.18
Net income per share, diluted	0.23		0.23		0.19		0.18

(1) We acquired 100% of the outstanding stock of GTI on November 11, 2013 and therefore our operating results for the fourth quarter of 2013 includes the operating results of GTI for the period of November, 11, 2013 to December 31, 2013.