Summarized Quarterly Financial Data

12 Months Ended

Dec. 31, 2011

Summarized Quarterly Financial Data [Abstract]

16. Summarized Quarterly Financial Data (Unaudited)

	Quarter Ended
(Thousands of Dollars)	March 31, 2011			June 30, 2011			Sept. 30, 2011			Dec. 31, 2011
Operating revenues		$	1,144,447		$	933,100		$	1,063,934		$	1,099,321
Operating income			195,308			153,176			266,422			179,026
Net income			96,630			71,018			140,718			88,437

	Quarter Ended
(Thousands of Dollars)	March 31, 2010			June 30, 2010			Sept. 30, 2010			Dec. 31, 2010
Operating revenues		$	1,202,697		$	947,296		$	954,970		$	1,059,407
Operating income			201,078			156,677			243,055			154,242
Net income			84,250			77,685			158,091			79,694

- Definition

The entire disclosure for the quarterly financial data in the annual financial statements. The disclosure may include a tabular presentation of financial information for each fiscal quarter for the current and previous year, including revenues, gross profit, income or loss before extraordinary items and earnings per share data. It also includes an indication if the information in the note is unaudited, comments on the aggregate effect of year-end adjustments, and an explanation of matters or transactions that affect comparability or are pertinent to an understanding of the information furnished.

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