Fair value measurements (Tables)

9 Months Ended

Sep. 30, 2015

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

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

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

(U.S. Dollars, in thousands)	Balance September 30, 2015			Level 1		Level 2			Level 3
Assets
Collective trust funds	$	1,622		$	—	$	1,622		$	—
Treasury securities		518			518		—			—
Certificates of deposit		594			594		—			—
Derivative securities		4,944			—		4,944			—
Equity securities		1,457			—		1,457			—
Debt securities		15,694			—		—			15,694
Total	$	24,829		$	1,112	$	8,023		$	15,694
Liabilities
Deferred compensation plan	$	(1,554	)	$	—	$	(1,554	)	$	—
Total	$	(1,554	)	$	—	$	(1,554	)	$	—

(U.S. Dollars, in thousands)	Balance December 31, 2014			Level 1		Level 2			Level 3
Assets
Collective trust funds	$	1,696		$	—	$	1,696		$	—
Treasury securities		586			586		—			—
Certificates of deposit		1,510			1,510		—			—
Derivative securities		2,825			—		2,825			—
Equity securities		1,457			—		1,457			—
Total	$	8,074		$	2,096	$	5,978		$	—
Liabilities
Deferred compensation plan	$	(1,886	)	$	—	$	(1,886	)	$	—
Total	$	(1,886	)	$	—	$	(1,886	)	$	—

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)	2015
Balance at January 1	$	—
Additions to debt securities		15,000
Accrued interest income		694
Balance at September 30	$	15,694