Credit Facilities (Tables)

12 Months Ended

Dec. 31, 2018

Line of Credit Facility [Line Items]

Summary Of Costs Incurred Connection With Credit Facilities

	Years Ended December 31,
(Dollars in thousands)	2018		2017		2016
Credit facility fees incurred	$	420	$	420	$	793

Wells Fargo Bank Group Credit Facility [Member]

Line of Credit Facility [Line Items]

Summary Of Outstanding Letters Of Credit And/Or Borrowings

(Dollars in thousands)		At December 31, 2018					At December 31, 2017
Bank		Commitment		In Use		Date of Expiry	Commitment		In Use		Date of Expiry
Wells Fargo Bank Group Credit Facility	Tranche One	$	200,000	$	-		$	200,000	$	-
	Tranche Two		600,000		558,818	12/31/2019		600,000		538,214	12/31/2018
Total Wells Fargo Bank Group Credit Facility		$	800,000	$	558,818		$	800,000	$	538,214

Citibank Bilateral Agreement [Member]

Line of Credit Facility [Line Items]

Summary Of Outstanding Letters Of Credit And/Or Borrowings

(Dollars in thousands)	At December 31, 2018					At December 31, 2017
Bank	Commitment		In Use		Date of Expiry	Commitment		In Use		Date of Expiry
Citibank Bilateral Letter of Credit Agreement	$	200,000	$	3,482	2/28/2019	$	250,000	$	3,297	2/28/2018
				3,672	11/24/2019				3,672	11/24/2018
				72,443	12/31/2019				73,626	12/31/2018
				296	8/15/2020				344	8/30/2019
				177	12/16/2020				93,855		12/30/2021
				125	12/20/2020				-
				1,851	11/4/2022				-
				407	11/13/2022				-
				59,293	12/30/2022				-
Total Citibank Bilateral Agreement	$	200,000	$	141,746		$	250,000	$	174,794

Lloyds Bank plc Credit Facility [Member]

Line of Credit Facility [Line Items]

Summary Of Outstanding Letters Of Credit And/Or Borrowings

(Dollars in thousands)	At December 31, 2018					At December 31, 2017
Bank	Commitment		In Use		Date of Expiry	Commitment		In Use		Date of Expiry
Lloyd's Bank plc	£	30,000	£	26,000	12/31/2022	£	145,000	£	-
		-		-			-		-
Total Lloyd's Bank Credit Facility	£	30,000	£	26,000		£	145,000	£	-