Commitments: (Tables)

12 Months Ended

Dec. 31, 2018

Commitments:

Schedule of estimated minimum rental commitments

As of December 31, 2018, our estimated minimum rental commitments are as follows:

	(dollars inthousands)
2019	$	3,730
2020		1,413
2021		798
2022		608
2023		386
Thereafter		1,157

Schedule of estimated minimum long-term commitments

As of December 31, 2018, our estimated commitments are as follows:

	(dollars in thousands)
					Gas		Maintenance		Asset Retirement
	Coal		Nuclear Fuel		Transportation		Agreements		Obligations
2019	$	22,065	$	49,100	$	64,497	$	29,510	$	8,664
2020		7,091		27,500		63,260		53,911		11,274
2021		2,348		30,300		62,737		14,461		11,215
2022		—		25,400		53,796		14,929		11,200
2023		—		18,400		47,513		3,330		37,743
Thereafter		—		35,100		848,609		281,938		3,536,362