Credit Facilities (Tables)

12 Months Ended

Dec. 31, 2019

Line of Credit Facility [Line Items]

Summary Of Costs Incurred Connection With Credit Facilities

	Years Ended December 31,
(Dollars in thousands)	2019		2018		2017
Credit facility interest and fees incurred	$	420	$	420	$	420

Wells Fargo Bank Group Credit Facility [Member]

Line of Credit Facility [Line Items]

Summary Of Outstanding Letters Of Credit And Borrowings

(Dollars in thousands)		At December 31, 2019					At December 31, 2018
Bank		Commitment		In Use		Date of Expiry	Commitment		In Use		Date of Expiry
Wells Fargo Bank Group Credit Facility	Tranche One	$	200,000	$	33,737	12/31/2020	$	200,000	$	-
	Tranche Two				2,381	7/29/2020
	Tranche Two				1,649	9/30/2020
	Tranche Two				573,353	12/31/2020
	Tranche Two		600,000		12,364	1/4/2021		600,000		558,818	12/31/2019
Total Wells Fargo Bank Group Credit Facility		$	800,000	$	623,484		$	800,000	$	558,818

Citibank Bilateral Agreement [Member]

Line of Credit Facility [Line Items]

Summary Of Outstanding Letters Of Credit And Borrowings

(Dollars in thousands)	At December 31, 2019					At December 31, 2018
Bank	Commitment		In Use		Date of Expiry	Commitment		In Use		Date of Expiry
Citibank Bilateral Letter of Credit Agreement	$	200,000	$	4,425	02/29/2020	$	200,000	$	3,482	02/28/2019
				512	09/03/2020				3,672	11/24/2019
				3,672	11/24/2020				72,443	12/31/2019
				177	12/16/2020				296	08/15/2020
				125	12/20/2020				177	12/16/2020
				101,404	12/31/2020				125	12/20/2020
				559	08/15/2021				1,851	11/04/2022
				37,096	12/30/2023				407	11/13/2022
				-					59,293	12/30/2022
Total Citibank Bilateral Agreement	$	200,000	$	147,970		$	200,000	$	141,746

Lloyds Bank plc Credit Facility [Member]

Line of Credit Facility [Line Items]

Summary Of Outstanding Letters Of Credit And Borrowings

(Dollars in thousands)	At December 31, 2019					At December 31, 2018
Bank	Commitment		In Use		Date of Expiry	Commitment		In Use		Date of Expiry
Lloyd's Bank plc	£	47,000	£	47,000	12/31/2023	£	30,000	£	26,000	12/31/2022
		-		-			-		-
Total Lloyd's Bank Credit Facility	£	47,000	£	47,000		£	30,000	£	26,000