Employee Retirement Plans (Tables)

9 Months Ended

Sep. 30, 2011

Employee Retirement Plans [Abstract]

Components of net pension and postretirement benefits costs

	Three Months						Nine Months
	ended September 30,						ended September 30,
(millions)	2011			2010			2011			2010
Pension:
Service cost of benefits earned	$	7		$	7		$	21		$	20
Interest cost on projected benefit obligation		15			16			47			48
Expected return on plan assets		(16	)		(16	)		(49	)		(49	)
Net amortization		7			3			20			11
Net pension cost	$	13		$	10		$	39		$	30
Postretirement:
Service cost of benefits earned	$	1		$	1		$	4		$	5
Interest cost on projected benefit obligation		3			4			10			13
Net amortization		(5	)		(4	)		(16	)		(13	)
Net postretirement cost	$	(1	)	$	1		$	(2	)	$	5