Fair Value (Tables)

9 Months Ended

Sep. 30, 2019

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



	Fair Value Measurements at Reporting Date Using

			Quoted Prices in		Significant Other		Significant
			Active Markets for		Observable		Unobservable
			Identical Assets		Inputs		Inputs
	September 30, 2019		(Level 1)		(Level 2)		(Level 3)
	(dollars in thousands)
Nuclear decommissioning trust funds:
Domestic equity	$	164,319	$	164,319	$	—	$	—
International equity trust		88,037		—		88,037		—
Corporate bonds and debt		62,039		—		62,039		—
US Treasury securities		53,744		53,744		—		—
Mortgage backed securities		54,803		—		54,803		—
Domestic mutual funds		50,990		50,990		—		—
Municipal bonds		1,237		—		1,237		—
Federal agency securities		2,197		—		2,197		—
Non-US Gov't bonds & private placements		272		—		272		—
Other		5,597		5,597		—		—
Long-term investments:
International equity trust		21,190		—		21,190		—
Corporate bonds and debt		18,340		—		18,340		—
US Treasury securities		9,772		9,772		—		—
Mortgage backed securities		13,246		—		13,246		—
Domestic mutual funds		94,772		94,772		—		—
Federal agency securities		46		—		46		—
Treasury STRIPS		48,058		—		48,058		—
Other		2,600		2,600		—		—
Natural gas swaps		26,379		—		26,379		—



	Fair Value Measurements at Reporting Date Using

			Quoted Prices in		Significant Other		Significant
			Active Markets for		Observable		Unobservable
			Identical Assets		Inputs		Inputs
	December 31, 2018		(Level 1)		(Level 2)		(Level 3)
	(dollars in thousands)
Nuclear decommissioning trust funds:
Domestic equity	$	136,196	$	136,196	$	—	$	—
International equity trust		76,852		—		76,852		—
Corporate bonds and debt		51,356		—		48,853		2,503
US Treasury securities		47,712		47,712		—		—
Mortgage backed securities		56,004		—		56,004		—
Domestic mutual funds		43,359		43,359		—		—
Municipal bonds		278		—		278		—
Federal agency securities		6,066		—		6,066		—
Non-US Gov't bonds & private placements		964		—		964		—
Other		2,031		2,031		—		—
Long-term investments:
International equity trust		17,382		—		17,382		—
Corporate bonds and debt		12,571		—		11,366		1,205
US Treasury securities		12,062		12,062		—		—
Mortgage backed securities		11,517		—		11,517		—
Domestic mutual funds		94,494		94,494		—		—
Federal agency securities		941		—		941		—
Treasury STRIPS		14,113		—		14,113		—
Other		1,045		1,045		—		—
Natural gas swaps		13,154		—		13,154		—

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



	Three Months Ended
	September 30, 2019

	Corporate bonds and debt
	(dollars in thousands)
Assets (Liabilities):
Balance at June 30, 2019	$	—
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)		—
Liquidations		—
Balance at September 30, 2019	$	—



	Nine Months Ended
	September 30, 2019

	Corporate bonds and debt
	(dollars in thousands)
Assets (Liabilities):
Balance at December 31, 2018	$	3,708
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)		94
Liquidations		(3,802)
Balance at September 30, 2019	$	—



	Three Months Ended
	September 30, 2018

	Corporate bonds and debt
	(dollars in thousands)
Assets (Liabilities):
Balance at June 30, 2018	$	4,997
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)		(656)
Balance at September 30, 2018	$	4,341



	Nine Months Ended
	September 30, 2018

	Corporate bonds and debt
	(dollars in thousands)
Assets (Liabilities):
Balance at December 31, 2017	$	—
Transfers to Level 3		4,997
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)		(656)
Balance at September 30, 2018	$	4,341

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 September 30, 2019 and December 31, 2018 were as follows (in thousands):



	2019				2018
	Carrying Value		Fair Value		Carrying Value		Fair Value
Long-term debt	$	9,174,752	$	10,976,451	$	9,347,307	$	9,837,254