Fair value measurements (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2015			Level 1		Level 2			Level 3
Assets
Collective trust funds	$	1,679		$	—	$	1,679		$	—
Treasury securities		507			507		—			—
Certificates of deposit		1,260			1,260		—			—
Derivative securities		6,472			—		6,472			—
Equity securities		1,457			—		1,457			—
Debt securities		15,000			—		—			15,000
Total	$	26,375		$	1,767	$	9,608		$	15,000
Liabilities
Deferred compensation plan	$	(1,488	)	$	—	$	(1,488	)	$	—
Total	$	(1,488	)	$	—	$	(1,488	)	$	—

(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 the 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
Balance at March 31	$	15,000