Components of Net Periodic Benefit Cost (Tables)

6 Months Ended

Jun. 30, 2015

Text Block [Abstract]

Schedule of Components of Net Periodic Benefit Costs

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 June 30,
	Three Months						Six Months						Twelve Montls
	2015			2014			2015			2014			2015			2014
(Thousands of dollars)
Service cost	$	6,281		$	5,340		$	12,561		$	10,680		$	23,241		$	22,208
Interest cost		11,057			10,860			22,115			21,721			43,834			40,525
Expected return on plan assets		(14,452	)		(13,335	)		(28,904	)		(26,671	)		(55,575	)		(51,591	)
Amortization of net actuarial loss		8,186			5,718			16,371			11,436			27,808			27,566
Net periodic benefit cost	$	11,072		$	8,583		$	22,143		$	17,166		$	39,308		$	38,708
	SERP
	Period Ended June 30,
	Three Months						Six Months						Twelve Montls
	2015			2014			2015			2014			2015			2014
(Thousands of dollars)
Service cost	$	80		$	73		$	160		$	146		$	306		$	332
Interest cost		424			436			847			872			1,720			1,640
Amortization of net actuarial loss		323			196			647			392			1,038			877
Net periodic benefit cost	$	827		$	705		$	1,654		$	1,410		$	3,064		$	2,849
	PBOP
	Period Ended June 30,
	Three Months						Six Months						Twelve Montls
	2015			2014			2015			2014			2015			2014
(Thousands of dollars)
Service cost	$	410		$	275		$	821		$	551		$	1,371		$	1,161
Interest cost		750			708			1,499			1,415			2,913			2,656
Expected return on plan assets		(866	)		(816	)		(1,732	)		(1,632	)		(3,364	)		(3,044	)
Amortization of prior service costs		334			88			667			177			845			355
Amortization of net actuarial loss		86			—			173			—			173			472
Net periodic benefit cost	$	714		$	255		$	1,428		$	511		$	1,938		$	1,600