Debt - Summary of Interest Rate Swaps Activity Recorded in Other Comprehensive Income Before Tax (Details 3) - Interest Rate Swap - Designated as Hedging Instrument - Cash Flow Hedge - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest rate swap activity recorded in Other comprehensive earnings before tax
Unrealized (loss) gain	$ (255)	$ 593	$ (516)
Interest Expense
Interest rate swap activity recorded in Other comprehensive earnings before tax
Realized gain reclassified to interest expense	$ 37	$ 928	$ 768