Fair value measurements (Tables)

3 Months Ended

Mar. 31, 2017

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:

	March 31, 2017										December 31, 2016
(U.S. Dollars, in thousands)	Level 1		Level 2			Level 3		Total			Total
Assets
Collective trust funds	$	—	$	1,583		$	—	$	1,583		$	1,584
Treasury securities		466		—			—		466			467
Certificates of deposit		—		—			—		—			468
Debt securities		—		—			9,000		9,000			12,220
Total	$	466	$	1,583		$	9,000	$	11,049		$	14,739
Liabilities
Deferred compensation plan	$	—	$	(1,207	)	$	—	$	(1,207	)	$	(1,452	)
Total	$	—	$	(1,207	)	$	—	$	(1,207	)	$	(1,452	)

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)	2017			2016
Balance at January 1	$	12,220		$	12,658
Accrued interest income		—			316
Gains or losses recorded for the period
Recognized in net income		(5,585	)		—
Recognized in other comprehensive income		2,365			(824	)
Balance at March 31	$	9,000		$	12,150