Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Statement of Other Comprehensive Income [Abstract]
Net income	$ 214	$ 226	$ 414	$ 462
Pension and postretirement benefits other than pensions:
Net loss arising during the period, net of income tax benefit of $3 for both the three- and six-month periods ended June 30, 2012.	(4)	0	(4)	0
Amortization of net loss included in net income, net of income tax expense of $1and $1 for the three months ended June 30, 2012 and 2011, respectively and $3 and $1 for the six months ended June 30, 2012 and 2011 respectively	1	1	4	2
Comprehensive income	$ 211	$ 227	$ 414	$ 464