Fair Value Measurements - Schedule of Assets and Liabilities Carried at Fair Value Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Municipal notes and bonds	$ 91,339	$ 87,029
Corporate bonds		843
Foreign currency forward contracts	61	312
Total Assets	91,400	88,184
Contingent consideration - acquisitions	3,025	3,251
Total Liabilities	3,025	3,251
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Municipal notes and bonds	0	0
Corporate bonds		0
Foreign currency forward contracts	0	0
Total Assets	0	0
Contingent consideration - acquisitions	0	0
Total Liabilities	0	0
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Municipal notes and bonds	91,339	87,029
Corporate bonds		843
Foreign currency forward contracts	61	312
Total Assets	91,400	88,184
Contingent consideration - acquisitions	0	0
Total Liabilities	0	0
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Municipal notes and bonds	0	0
Corporate bonds		0
Foreign currency forward contracts	0	0
Total Assets	0	0
Contingent consideration - acquisitions	3,025	3,251
Total Liabilities	$ 3,025	$ 3,251