Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Selected Quarterly Financial Data (Unaudited) [Abstract]

Selected Quarterly Financial Data

	First		Second		Third		Fourth		Year
2016
Operating revenues	$	11,278	$	11,820	$	12,601	$	11,885	$	47,584
Operating income		5,214		5,695		6,414		5,565		22,888
Net income		2,486		2,847		3,571		2,942		11,846
Basic earnings per share		0.19		0.23		0.27		0.23		0.92
Diluted earnings per share		0.19		0.23		0.27		0.23		0.92
Dividends declared per share		0.1555		0.1555		0.1555		0.1602		0.6267
2015
Operating revenues	$	11,209	$	11,895	$	12,368	$	11,617	$	47,089
Operating income		5,134		5,682		6,353		5,492		22,661
Net income		2,528		2,925		3,520		3,516		12,489
Basic earnings per share		0.20		0.22		0.28		0.27		0.97
Diluted earnings per share		0.20		0.22		0.28		0.27		0.97
Dividends declared per share		0.1495		0.1495		0.1495		0.1555		0.6040