Notes Payable and Debt and Financing Arrangements (Tables)

12 Months Ended

Dec. 31, 2015

Debt Disclosure [Abstract]

Financing structure

The following table presents the Company's outstanding notes payable and debt as of December 31, 2015 and 2014:

(U.S. dollars in thousands)	2015				2014
	Commitment/ Debt (1)		In Use/ Outstanding (2)		Commitment/ Debt (1)		In Use/ Outstanding (2)
Debt:
2.30% Senior Notes due 2018	$	300,000	$	298,015	$	300,000	$	297,344
5.75% Senior Notes due 2021	400,000		397,523		400,000		397,092
6.375% Senior Notes due 2024	350,000		349,029		350,000		348,920
4.45% Subordinated Notes due 2025	500,000		492,521		—		—
6.25% Senior Notes due 2027	325,000		323,218		325,000		323,062
5.25% Senior Notes due 2043	300,000		296,294		300,000		296,162
5.5% Subordinated Notes due 2045	500,000		488,370		—		—
Total debt carrying value	$	2,675,000	$	2,644,970	$	1,675,000	$	1,662,580

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(1) Excluded from the table are certain credit facilities under which the Company is permitted to utilize up to $1.4 billion and $1.6 billion as of December 31, 2015 and December 31, 2014, respectively, for revolving loans to support general operating and financing needs. However, as of December 31, 2015 and December 31, 2014, $527.1 million and $606.1 million, respectively, were utilized under these facilities to issue letters of credit, leaving $822.9 million and $968.9 million, respectively, available to support other operating and financing needs.

(2)    "In Use/Outstanding" data represent December 31, 2015 and December 31, 2014 accreted values.

Credit facilities

The Company’s available credit facilities at December 31 were as follows:

(U.S. dollars in thousands)	2015 (1)			2014 (1)
Total available credit facilities – commitments (2)	$	4,463,041		$	3,575,000
Letters of credit – in use	$	2,515,653		$	1,790,561
Collateralized by certain assets of the Company’s investment portfolio	50.9		%	66.2		%

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(1) As of December 31, 2015 and December 31, 2014, there were fifteen and eight available credit facilities, respectively.

(2) As of December 31, 2015 and December 31, 2014 the stated portion of allowable credit facilities permitted to be utilized for revolving loans was $1.4 billion and $1.6 billion, respectively. However, as of December 31, 2015 and December 31, 2014, $527.1 million and $606.1 million, respectively, of such facilities' limits were utilized to issue letters of credit, leaving $822.9 million and $968.9 million, respectively, available either to issue additional letters of credit or to support other operating or financing needs under these particular facilities.