Fair Value (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value

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
	March 31, 2019		(Level 1)		(Level 2)		(Level 3)
	(dollars in thousands)
Nuclear decommissioning trust funds:
Domestic equity	$	154,952	$	154,952	$	—	$	—
International equity trust		86,813		—		86,813		—
Corporate bonds and debt		57,108		—		56,297		811
US Treasury securities		51,850		51,850		—		—
Mortgage backed securities		51,222		—		51,222		—
Domestic mutual funds		50,292		50,292		—		—
Municipal bonds		425		—		425		—
Federal agency securities		3,942		—		3,942		—
Non-US Gov't bonds & private placements		1,425		—		1,425		—
Other		4,014		4,014		—		—
Long-term investments:
International equity trust		20,885		—		20,885		—
Corporate bonds and debt		11,658		—		11,152		506
US Treasury securities		14,277		14,277		—		—
Mortgage backed securities		11,791		—		11,791		—
Domestic mutual funds		94,326		94,326		—		—
Federal agency securities		934		—		934		—
Treasury STRIPS		23,677		—		23,677		—
Other		638		638		—		—
Natural gas swaps		8,867		—		8,867		—

	FairValue 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
	March 31, 2019
	Corporate bonds and debt
	(dollars in thousands)
Balance at December 31, 2018	$	3,708
Total gains or losses (realized/unrealized):
Changes in net assets		(2,391)
Balance at March 31, 2019	$	1,317

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

	2019				2018
	Carrying Value		Fair Value		Carrying Value		Fair Value
Long-term debt	$	9,209,076	$	10,003,168	$	9,347,307	$	9,837,254