Fair Value (Tables)

6 Months Ended

Jun. 30, 2015

Fair Value

Schedule of assets and liabilities measured at fair value on a recurring basis

	Fair Value Measurements at Reporting Date Using
		June 30, 2015		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
		(dollars in thousands)
Nuclear decommissioning trust funds:
Domestic equity	$	155,440	$	155,440	$	—	$	—
International equity trust		74,017		—		74,017		—
Corporate bonds		38,834		—		38,834		—
US Treasury and government agency securities		75,625		75,625		—		—
Agency mortgage and asset backed securities		16,108		—		16,108		—
Municipal bonds		916		—		916		—
Other		12,296		12,296		—		—
Long-term investments:
International equity trust		12,566		—		12,566		—
Corporate bonds		6,179		—		6,179		—
US Treasury and government agency securities		16,781		16,781		—		—
Agency mortgage and asset backed securities		926		—		926		—
Mutual funds		48,172		48,172		—		—
Other		209		209		—		—
Interest rate options		4,715		—		—		4,715
Natural gas swaps		15,942		—		15,942		—

	Fair Value Measurements at Reporting Date Using
		December 31, 2014		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
		(dollars in thousands)
Nuclear decommissioning trust funds:
Domestic equity	$	159,536	$	159,536	$	—	$	—
International equity trust		72,474		—		72,474		—
Corporate bonds		34,446		—		34,446		—
US Treasury and government agency securities		68,854		68,854		—		—
Agency mortgage and asset backed securities		16,148		—		16,148		—
Municipal Bonds		743		—		743		—
Other		13,803		13,803		—		—
Long-term investments:
Corporate bonds		5,445		—		5,445		—
US Treasury and government agency securities		16,619		16,619		—		—
Agency mortgage and asset backed securities		643		—		643		—
International equity trust		11,162		—		11,162		—
Mutual funds		51,741		51,741		—		—
Other		118		118		—		—
Interest rate options		4,371		—		—		4,371
Natural gas swaps		18,914		—		18,914		—

Schedule of changes in Level 3 assets and liabilities measured at fair value on a recurring basis

		Three Months Ended June 30, 2015
		Interest rate options
		(dollars in thousands)
Assets (Liabilities):
Balance at March 31, 2015	$	2,702
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)		2,013
Balance at June 30, 2015	$	4,715

		Three Months Ended June 30, 2014
		Interest rate options
		(dollars in thousands)
Assets (Liabilities):
Balance at March 31, 2014	$	31,463
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)		(12,928	)
Balance at June 30, 2014	$	18,535

		Six Months Ended June 30, 2015
		Interest rate options
		(dollars in thousands)
Assets (Liabilities):
Balance at December 31, 2014	$	4,371
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)		344
Balance at June 30, 2015	$	4,715

		Six Months Ended June 30, 2014
		Interest rate options
		(dollars in thousands)
Assets (Liabilities):
Balance at December 31, 2013	$	63,471
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)		(44,936	)
Balance at June 30, 2014	$	18,535

Schedule of estimated fair values of long term debt, including current maturities

The estimated fair values of our long-term debt, including current maturities at June 30, 2015 and December 31, 2014 were as follows (in thousands):

		2015				2014
		Carrying Value		Fair Value		Carrying Value		Fair Value
Long-term debt	$	7,476,491	$	8,281,385	$	7,256,995	$	8,460,685