Selected Quarterly Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2011

Selected Quarterly Data (Unaudited) Tables [Abstract]

Selected Quarterly Data (Unaudited) [Table Text Block]

19. Selected Quarterly Data (Unaudited)

Millions, Except Per Share Amounts
2011	Mar. 31		Jun. 30		Sep. 30		Dec. 31
Operating revenues	$	4,490	$	4,858	$	5,101	$	5,108
Operating income		1,137		1,392		1,578		1,617
Net income		639		785		904		964
Net income per share:
Basic		1.31		1.61		1.87		2.01
Diluted		1.29		1.59		1.85		1.99
Millions, Except Per Share Amounts
2010	Mar. 31		Jun. 30		Sep. 30		Dec. 31
Operating revenues	$	3,965	$	4,182	$	4,408	$	4,410
Operating income		988		1,279		1,401		1,313
Net income		516		711		778		775
Net income per share:
Basic		1.02		1.42		1.58		1.58
Diluted		1.01		1.40		1.56		1.56