Subsequent Events (Details) - USD ($)		9 Months Ended
	Nov. 05, 2018	Sep. 30, 2018	Dec. 31, 2017	May 04, 2017	May 03, 2017	Jan. 19, 2010
Subsequent Event [Line Items]
Business Acquisition Obligation Current		$ 3,992,000	$ 3,759,000
Treasury Stock, Shares, Acquired		8,600,000
Common Stock, Shares, Outstanding		23,611,680	22,419,417
Subsequent Event
Subsequent Event [Line Items]
Unrestricted Domestic Cash Holdings	100.00%
Unrestricted Foreign Cash Holdings	70.00%
Restricted Payments, Redemption, Purchases Or Repurchases	$ 5,000,000
Stock Repurchase Program, Authorized Amount, Increase	15,000,000
Stock Repurchase Program, Authorized Amount	75,000,000
Treasury Stock, Value, Acquired, Cost Method	$ 44,500,000
Common Stock, Shares, Outstanding	23,600,000.0
Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 35,000,000.0	$ 20,000,000.0	$ 15,000,000.0
Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member] | Subsequent Event
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 5,000,000.0
Business Acquisition Obligations [Member]
Subsequent Event [Line Items]
Business Acquisition Obligation Current		$ 4,000,000	$ 8,900,000