Line of Credit (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	May. 07, 2014
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 125.0		$ 90.0
Line of Credit Facility Maximum Borrowing Capacity Increase	35.0
Line of credit facility, commitment increase	50.0	$ 25.0
Line of credit facility, allowable issuance amount of letters of credit	10.0
Letters of credit outstanding	$ 0.2
Credit agreement, final maturity date	Jul. 31, 2017
Line of credit, interest rate at period end (in hundredths)	0.19%
Line of credit facility, percentage of annual commitment fee on unused capacity (in hundredths)	0.20%
Unused portion of line of credit	$ 63.8
Minimum [Member]
Line of Credit Facility [Line Items]
Line of credit, margin interest rate percentage (in hundredths)	2.00%
Ratio of EBITDA plus stock compensation and minus income taxes paid and capital expenditures to interest expense and scheduled payments due for borrowings	1.00
Ratio of current maturities of long-term debt to EBITDA plus stock compensation and minus income taxes paid and capital expenditures	1.00
Maximum [Member]
Line of Credit Facility [Line Items]
Line of credit, margin interest rate percentage (in hundredths)	2.50%
Ratio of EBITDA plus stock compensation and minus income taxes paid and capital expenditures to interest expense and scheduled payments due for borrowings	2.00
Ratio of current maturities of long-term debt to EBITDA plus stock compensation and minus income taxes paid and capital expenditures	2.75
Silicon Valley Bank [Member]
Line of Credit Facility [Line Items]
Line of credit, interest rate at period end (in hundredths)	4.00%
Silicon Valley Bank [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of credit, margin interest rate percentage (in hundredths)	0.00%
Silicon Valley Bank [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Line of credit, margin interest rate percentage (in hundredths)	0.50%