Employee Retirement Plans (Tables)

6 Months Ended

Jun. 30, 2011

Employee Retirement Plans [Abstract]

Components of net pension and postretirement benefits costs

	Three Months						Six Months
	ended June 30,						ended June 30,
(millions)	2011			2010			2011			2010
Pension:
Service cost of benefits earned	$	7		$	6		$	14		$	13
Interest cost on projected benefit obligation		16			16			32			32
Expected return on plan assets		(17	)		(16	)		(33	)		(33	)
Net amortization		7			4			13			8
Net pension cost	$	13		$	9		$	26		$	20
Postretirement:
Service cost of benefits earned	$	1		$	2		$	3		$	4
Interest cost on projected benefit obligation		3			5			7			9
Net amortization		(5	)		(5	)		(11	)		(9	)
Net postretirement cost	$	(1	)	$	2		$	(1	)	$	4