Benefit Plans and Other Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2013

Compensation and Retirement Disclosure [Abstract]

Components of Net Periodic Benefit Cost

Components of Net Periodic Benefit Cost

	Three Months Ended June 30
	2013			2012			2013			2012
(Thousands of Dollars)	Pension Benefits						Postretirement Health Care Benefits
Service cost	$	24,070		$	21,853		$	1,182		$	922
Interest cost	35,173			39,365			8,417			9,551
Expected return on plan assets	(49,613		)	(52,072		)	(8,253		)	(7,094		)
Amortization of transition obligation	—			—			206			3,580
Amortization of prior service cost (credit)	1,468			5,267			(2,438		)	(1,888		)
Amortization of net loss	36,038			27,467			5,646			4,487
Net periodic benefit cost	47,136			41,880			4,760			9,558
Costs not recognized and additional cost recognized due to the effects of regulation	(7,089		)	(10,158		)	—			973
Net benefit cost recognized for financial reporting	$	40,047		$	31,722		$	4,760		$	10,531

	Six Months Ended June 30
	2013			2012			2013			2012
(Thousands of Dollars)	Pension Benefits						Postretirement Health Care Benefits
Service cost	$	48,141		$	43,182		$	2,364		$	2,102
Interest cost	70,345			78,088			16,834			18,931
Expected return on plan assets	(99,226		)	(103,548		)	(16,506		)	(14,205		)
Amortization of transition obligation	—			—			412			7,160
Amortization of prior service cost (credit)	2,936			10,533			(4,876		)	(3,776		)
Amortization of net loss	72,076			53,785			11,292			8,452
Net periodic benefit cost	94,272			82,040			9,520			18,664
Costs not recognized and additional cost recognized due to the effects of regulation	(14,936		)	(19,291		)	—			1,946
Net benefit cost recognized for financial reporting	$	79,336		$	62,749		$	9,520		$	20,610