Fair value measurements (Tables)

6 Months Ended

Jun. 30, 2016

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]

Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

The fair value of the Company’s financial assets and liabilities measured on a recurring basis were as follows:

(U.S. Dollars, in thousands)	June 30, 2016			Level 1		Level 2			Level 3
Assets
Collective trust funds	$	1,599		$	—	$	1,599		$	—
Treasury securities		521			521		—			—
Certificates of deposit		443			443		—			—
Derivative instruments		2,374			—		2,374			—
Debt securities		9,438			—		—			9,438
Total	$	14,375		$	964	$	3,973		$	9,438
Liabilities
Deferred compensation plan	$	(1,488	)	$	—	$	(1,488	)	$	—
Total	$	(1,488	)	$	—	$	(1,488	)	$	—

(U.S. Dollars, in thousands)	December 31, 2015			Level 1		Level 2			Level 3
Assets
Collective trust funds	$	1,622		$	—	$	1,622		$	—
Treasury securities		495			495		—			—
Certificates of deposit		337			337		—			—
Derivative instruments		2,485			—		2,485			—
Debt securities		12,658			—		—			12,658
Total	$	17,597		$	832	$	4,107		$	12,658
Liabilities
Deferred compensation plan	$	(1,503	)	$	—	$	(1,503	)	$	—
Total	$	(1,503	)	$	—	$	(1,503	)	$	—

Fair Value, Inputs, Level 3 [Member]

Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]

Schedule of Reconciliation of Available for Sale Debt Securities

The following table provides a reconciliation of the beginning and ending balances for debt securities measured at fair value using significant unobservable inputs (Level 3):

(U.S. Dollars, in thousands)
Balance at December 31, 2015	$	12,658
Accrued interest income		640
Unrealized loss on debt securities		(3,860	)
Balance at June 30, 2016	$	9,438