Financial instruments (Tables)

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Instruments in Statement of Financial Position, Fair Value

The following table presents the locations in the consolidated balance sheets and fair value of derivative instruments as of December 31, 2018 and 2017:



	December 31, 2018		December 31, 2017
	Fair Value
	(Dollars in thousands)
Asset derivatives:
Designated foreign currency forward contracts	$	1,216	$	914
Non-designated foreign currency forward contracts	106		307
Cross-currency interest rate swap	14,728		—
Prepaid expenses and other current assets	16,050		1,221
Total asset derivatives	16,050		1,221
Liability derivatives:
Designated foreign currency forward contracts	524		1,373
Non-designated foreign currency forward contracts	264		53
Other current liabilities	788		1,426
Cross-currency interest rate swap	7,793		—
Other liabilities	7,793		—
Total liability derivatives	$	8,581	$	1,426

Aggregate Accounts Receivable, Net of Allowance for Doubtful Accounts

he aggregate net current and long-term trade accounts receivable related to customers in Greece, Italy, Spain and Portugal and the percentage of the Company’s total net current and long-term trade accounts receivable represented by these customers' trade accounts receivable at December 31, 2018 and 2017:



	December 31, 2018			December 31, 2017
	(Dollars in thousands)
Allowance for doubtful accounts ₍₁₎	$	9,348		$	10,255
Current and long-term trade accounts receivable in Greece, Italy, Spain and Portugal ₍₂₎	$	39,026		$	49,054
Percentage of total net current and long-term trade accounts receivables	11.0		%	14.6		%

(1) The current portion of the allowance for doubtful accounts was $4.4 million and $3.5 million as of December 31, 2018 and 2017, respectively, and was recognized in accounts receivable, net.

(2) The long-term portion of trade accounts receivable, net from customers in Greece, Italy, Spain and Portugal at December 31, 2018 and 2017 was $2.7 million and $3.3 million, respectively. In December 2018, the Company sold $12.7 million of receivables outstanding with publicly funded hospitals in Italy and Portugal for $12.6 million.