Investments: (Tables)

12 Months Ended

Dec. 31, 2018

Investments:

Summary of debt and equity securities

	(dollars in thousands)
	Gross Unrealized
2018	Cost		Gains		Losses		Fair Value
Equity	$	251,226	$	64,954	$	(9,105)	$	307,075
Debt		278,030		1,718		(4,955)		274,793
Other		3,075		—		—		3,075
Total	$	532,331	$	66,672	$	(14,060)	$	584,943
	(dollars in thousands)
	Gross Unrealized
2017	Cost		Gains		Losses		Fair Value
Equity	$	246,549	$	91,954	$	(4,064)	$	334,439
Debt		240,878		1,814		(2,262)		240,430
Other		10,807		1		—		10,808
Total	$	498,234	$	93,769	$	(6,326)	$	585,677

Schedule of contractual maturities of debt securities

	(dollars in thousands)
	2018				2017
	Cost		Fair Value		Cost		Fair Value
Due within one year	$	65,039	$	63,925	$	54,785	$	54,143
Due after one year through five years		62,293		61,924		53,050		52,834
Due after five years through ten years		50,606		49,855		51,367		51,600
Due after ten years		100,092		99,089		81,676		81,853
Total	$	278,030	$	274,793	$	240,878	$	240,430

Summary of realized gains and losses and proceeds from sales of securities

	(dollars in thousands)
	2018		2017		2016
Gross realized gains	$	14,268	$	35,523	$	19,934
Gross realized losses		(19,139)		(16,909)		(20,030)
Proceeds from sales		626,612		521,345		439,540

Schedule of investments in associated companies

	(dollars in thousands)
	2018		2017
National Rural Utilities Cooperative Finance Corporation (CFC)	$	24,061	$	24,056
CT Parts, LLC		10,236		10,243
Georgia Transmission Corporation		30,237		28,690
Georgia System Operations Corporation		9,250		8,500
Other		3,253		3,492
Total	$	77,037	$	74,981