Debt - Overdraft and Factoring Agreement (Details) kr in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018 NOK (kr)	Dec. 31, 2018 USD ($)
Factoring Agreement | DNB Bank
Line of Credit Facility [Line Items]
Required notice period for termination of the agreement by factor	14 days
DFBG Swims | Overdraft Agreement | DNB Bank | Maximum
Line of Credit Facility [Line Items]
Maximum borrowing capacity	kr 6.0	$ 0.7
DFBG Swims | Overdraft Agreement | Factoring, Second Lien | DNB Bank
Line of Credit Facility [Line Items]
Collateral amount	kr 0.4
DFBG Swims | Ordinary Credit
Line of Credit Facility [Line Items]
Number of days notice required for termination of agreement	14 days
DFBG Swims | Ordinary Credit | DNB Bank
Line of Credit Facility [Line Items]
Maximum borrowing capacity	kr 3.5
Annual rate on outstanding principal amount (as a percent)	7.40%	7.40%
Quarterly fee percent	0.40%	0.40%
DFBG Swims | Additional Credit | DNB Bank
Line of Credit Facility [Line Items]
Maximum borrowing capacity | $		$ 2.5
Annual rate on outstanding principal amount (as a percent)	4.90%	4.90%
Quarterly fee percent	0.50%	0.50%
DFBG Swims | Factoring Agreement | DNB Bank
Line of Credit Facility [Line Items]
Required notice period for termination of the agreement by factor	14 days
DFBG Swims | Factoring Agreement | DNB Bank | Maximum
Line of Credit Facility [Line Items]
Financing Percentage on preapproved outstanding invoiced receivables	80.00%	80.00%
DFBG Swims | Factoring Agreement | Machinery and Plant Lien | DNB Bank
Line of Credit Facility [Line Items]
Collateral amount	kr 10.0
DFBG Swims | Factoring Agreement | Machinery and Plant Lien | DNB Bank | Maximum
Line of Credit Facility [Line Items]
Collateral amount	10.0
DFBG Swims | Factoring Agreement | Inventory Lien | DNB Bank | Maximum
Line of Credit Facility [Line Items]
Collateral amount	10.0
DFBG Swims | Factoring Agreement | Factoring, First Lien | DNB Bank
Line of Credit Facility [Line Items]
Collateral amount	1.0
DFBG Swims | Factoring Agreement | Factoring, Second Lien | DNB Bank
Line of Credit Facility [Line Items]
Collateral amount	4.0
DFBG Swims | Factoring Agreement | Factoring, Third Lien | DNB Bank
Line of Credit Facility [Line Items]
Collateral amount	7.0
DFBG Swims | Factoring Agreement | Factoring, Fourth Lien | DNB Bank
Line of Credit Facility [Line Items]
Collateral amount	kr 2.5