Summarized Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Summarized Quarterly Financial Data (Unaudited)

18. Summarized Quarterly Financial Data (Unaudited)

	Quarter Ended
(Amounts in thousands, except per share data)	March 31, 2016		June 30, 2016		Sept. 30, 2016		Dec. 31, 2016
Operating revenues	$	2,772,273	$	2,499,849	$	3,040,147	$	2,794,651
Operating income	489,870		431,581		827,054		465,350
Net income	241,312		196,795		457,795		227,477
EPS total — basic	$	0.47	$	0.39	$	0.90	$	0.45
EPS total — diluted	0.47		0.39		0.90		0.45
Cash dividends declared per common share	0.34		0.34		0.34		0.34

	Quarter Ended
(Amounts in thousands, except per share data)	March 31, 2015		June 30, 2015		Sept. 30, 2015		Dec. 31, 2015
Operating revenues	$	2,962,219	$	2,515,134	$	2,901,312	$	2,645,821
Operating income	350,845		422,845		785,812		441,010
Net income	152,066		196,931		426,463		209,025
EPS total — basic	$	0.30	$	0.39	$	0.84	$	0.41
EPS total — diluted	0.30		0.39		0.84		0.41
Cash dividends declared per common share	0.32		0.32		0.32		0.32