Debt (Tables)

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments [Table Text Block]

The Company’s long-term debt consists of the following as of December 31, 2015 and 2014 (dollars in thousands):

	2015			2014
$400 million 6.20% Subordinated Debentures due 2042	$	400,000		$	400,000
$400 million Variable Rate Junior Subordinated Debentures due 2065	318,734			318,732
$400 million 4.70% Senior Notes due 2023	398,835			398,684
$400 million 5.00% Senior Notes due 2021	398,803			398,583
$400 million 6.45% Senior Notes due 2019	399,737			399,669
$300 million 5.625% Senior Notes due 2017	299,671			299,397
$100 million 4.09% Promissory Note due 2039	96,849			99,228
Sub-total	2,312,629			2,314,293
Unamortized issuance costs	(15,081		)	(16,589		)
Long-term Debt	$	2,297,548		$	2,297,704

Schedule of Maturities of Long-term Debt [Table Text Block]

Future principal payments due on long-term debt, excluding discounts, as of December 31, 2015, were as follows (dollars in thousands):

	Calendar Year
	2016		2017		2018		2019		2020		Thereafter
Long-term debt	$	2,268	$	302,573	$	2,681	$	402,792	$	2,909	$	1,603,428

Schedule of Line of Credit Facilities [Table Text Block]

The following table provides additional information on the Company’s existing committed credit facilities as of December 31, 2015 and 2014 (dollars in thousands):

			Amount Utilized(1) December 31,
Facility Capacity		Maturity Date	2015		2014		Basis of Fees
$	850,000	September 2019	$	313,659	$	204,774	Senior unsecured long-term debt rating
120,000		June 2019	85,040		80,040		Fixed
270,000		November 2017	270,000		270,000		Fixed
100,000		June 2017	68,657		81,747		Fixed
129,214 (2)		November 2016	66,154		74,623		Fixed
45,422 (2)		March 2019	45,422		80,961		Fixed
36,430 (2)		May 2018	36,430		28,612		Fixed

(1) Represents issued but undrawn letters of credit. There was no cash borrowed for the periods presented.

(2) Foreign currency denominated facility, amounts presented are in U.S. dollars.