Other Comprehensive Income (Loss) and Accumulated Other Comprehensive Loss - Components of Other Comprehensive Income and Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		$ 635,371	$ 573,130	$ 616,030	$ 566,004
Current period other comprehensive income (loss):
Total current period other comprehensive (loss) income		(568)	558	(2,276)	3,030
Balance		650,673	584,786	650,673	584,786
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		(11,074)	(9,343)	(7,638)	(11,815)
Reclassification of stranded tax effects due to adoption of accounting principle	[1]			(1,307)
Adjusted beginning balance				(8,945)
Current period other comprehensive income (loss):
Other comprehensive (loss) income before reclassifications		(255)	943	(2,530)	4,113
Effect of taxes	[2]	(142)	(613)	4	(1,311)
Total current period other comprehensive (loss) income		(397)	330	(2,526)	2,802
Balance		(11,471)	(9,013)	(11,471)	(9,013)
Gain on Sale of Interest Rate Hedge Agreement
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	[3]	2,431	2,175	2,158	2,175
Reclassification of stranded tax effects due to adoption of accounting principle	[1],[3]			478
Adjusted beginning balance	[3]			2,636
Current period other comprehensive income (loss):
Amounts reclassified from accumulated other comprehensive income	[3]	(180)		(480)
Effect of taxes	[2],[3]	47		142
Total current period other comprehensive (loss) income	[3]	(133)		(338)
Balance	[3]	2,298	2,175	2,298	2,175
Change in Fair Value of Interest Rate Hedge Agreements
Accumulated Other Comprehensive Income Loss [Line Items]
Balance	[4],[5]	1,067		441
Adjusted beginning balance	[4],[5]			441
Current period other comprehensive income (loss):
Other comprehensive (loss) income before reclassifications	[4],[5]	371	228	997	228
Amounts reclassified from accumulated other comprehensive income	[4],[5]	(41)		(41)
Effect of taxes	[2],[4],[5]	(368)		(368)
Total current period other comprehensive (loss) income	[4],[5]	(38)	228	588	228
Balance	[4],[5]	1,029	228	1,029	228
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income Loss [Line Items]
Balance		(7,576)	(7,168)	(5,039)	(9,640)
Reclassification of stranded tax effects due to adoption of accounting principle	[1]			(829)
Adjusted beginning balance				(5,868)
Current period other comprehensive income (loss):
Other comprehensive (loss) income before reclassifications		116	1,171	(1,533)	4,341
Amounts reclassified from accumulated other comprehensive income		(221)		(521)
Effect of taxes	[2]	(463)	(613)	(222)	(1,311)
Total current period other comprehensive (loss) income		(568)	558	(2,276)	3,030
Balance		$ (8,144)	$ (6,610)	$ (8,144)	$ (6,610)

[1] The Company has adjusted the balance at December 31, 2017 of accumulated other comprehensive loss for the stranded tax effects caused by the enactment of the Tax Act.

[2] The Company’s effective tax rate for the three and nine months ended September 30, 2018 and 2017 was 22.9% and 34.5% and 24.0% and 35.6%, respectively.

[3] Represents the fair value of an interest rate hedge agreement, designated as a cash flow hedge, which was sold on December 1, 2016. The fair value of the interest rate hedge agreement was recorded in other comprehensive income, net of tax, and will be reclassified to interest expense when earnings are impacted by the hedged items and as interest payments are made on the Credit Facility from January 31, 2018 to January 31, 2023.

[4] Represents the change in fair value of interest rate hedge agreements designated as a cash flow hedge. The fair value of the interest rate hedge agreements were recorded in other comprehensive income and will be reclassified to interest expense when earnings are impacted by the hedged items and as interest payments are made on the Credit Facility from August 31, 2018 to August 31, 2023.

[5] The fair value of the fixed interest rate swap asset is included in other assets on the consolidated balance sheet.