Components of Net Periodic Benefit Cost (Tables)

9 Months Ended

Sep. 30, 2013

Text Block [Abstract]

Schedule of Components of Net Periodic Benefit Costs

Net periodic benefit costs included in the table below are components of an overhead loading process associated with the cost of labor. The overhead process ultimately results in allocation of net periodic benefit costs to the same accounts to which productive labor is charged. As a result, net periodic benefit costs become components of various accounts, primarily operations and maintenance expense, net utility plant, and deferred charges and other assets.

	Qualified Retirement Plan
	Period Ended September 30,
	Three Months						Nine Months						Twelve Months
	2013			2012			2013			2012			2013			2012
(Thousands of dollars)
Service cost	$	5,764		$	5,080		$	17,292		$	15,239		$	22,372		$	19,671
Interest cost		9,402			9,567			28,205			28,700			37,771			38,019
Expected return on plan assets		(12,460	)		(11,445	)		(37,380	)		(34,335	)		(48,825	)		(44,364	)
Amortization of net actuarial loss		8,065			5,970			24,196			17,912			30,167			21,499
Net periodic benefit cost	$	10,771		$	9,172		$	32,313		$	27,516		$	41,485		$	34,825
	SERP
	Period Ended September 30,
	Three Months						Nine Months						Twelve Months
	2013			2012			2013			2012			2013			2012
(Thousands of dollars)
Service cost	$	93		$	69		$	280		$	206		$	348		$	260
Interest cost		384			407			1,151			1,221			1,559			1,663
Amortization of net actuarial loss		243			171			729			513			899			671
Net periodic benefit cost	$	720		$	647		$	2,160		$	1,940		$	2,806		$	2,594
	PBOP
	Period Ended September 30,
	Three Months						Nine Months						Twelve Months
	2013			2012			2013			2012			2013			2012
(Thousands of dollars)
Service cost	$	305		$	244		$	915		$	733		$	1,159		$	947
Interest cost		620			637			1,861			1,910			2,498			2,567
Expected return on plan assets		(706	)		(601	)		(2,118	)		(1,803	)		(2,719	)		(2,397	)
Amortization of prior service cost		89			—			266			—			266			—
Amortization of transition obligation		—			217			—			650			217			867
Amortization of net actuarial loss		236			257			709			773			967			921
Net periodic benefit cost	$	544		$	754		$	1,633		$	2,263		$	2,388		$	2,905