Quarterly Results of Operations (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

A summary of quarterly results of operations for the years ended December 31, 2017 and 2016 follows (in thousands, except for per share data):

	QUARTER ENDED
	DEC. 31,		SEPT. 30,			JUNE 30,		MAR. 31,		DEC. 31,		SEPT. 30,		JUNE 30,		MAR. 31,
	2017		2017			2017		2017		2016		2016		2016		2016
Operating revenue	$	192,803	$	184,511		$	174,888	$	167,576	$	169,733	$	181,967	$	178,033	$	180,965
Income from continuing operations	114,463		63,968			50,510		42,125		197,038		51,675		48,815		56,626
Discontinued operations	17,361		(2,809		)	2,308		2,119		3,253		4,059		2,242		2,437
Net income	131,824		61,159			52,818		44,244		200,291		55,734		51,057		59,063
Income per common share - basic (1)	0.87		0.41			0.35		0.29		1.33		0.37		0.34		0.39
Income per common share - diluted (1)	0.87		0.40			0.35		0.29		1.33		0.37		0.34		0.39

(1) The sum of quarterly financial data may vary from the annual data due to rounding.