Derivatives Derivative Financial Instruments - Naratives (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 item	Sep. 30, 2012 USD ($) item	Jun. 24, 2012 USD ($) item
Derivative [Line Items]
Unrealized Loss on Foreign Currency Derivatives, before Tax	$ 371
Derivative Asset	423
Foreign Currency Cash Flow Hedge Liability at Fair Value	30
Designated as Hedging Instrument | Interest Rate Swap
Derivative [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	(576)
Cash Flow Hedge | Designated as Hedging Instrument | Foreign currency hedges
Derivative [Line Items]
Foreign Currency Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months	318
Derivative, Notional Amount	15,700
Interest rate swap - cash flow hedge	$ (393)		$ 742	$ 601
Cash Flow Hedge | Designated as Hedging Instrument | Interest Rate Swap
Derivative [Line Items]
Derivative, Notional Amount		$ 50,000				$ 25,000	$ 50,000
Derivative, Number of Instruments Held | item					3	4	4
Interest rate swap - cash flow hedge			$ (971)	$ (753)