Debt (Details)							1 Months Ended	9 Months Ended		12 Months Ended
	May 04, 2017 USD ($)	Feb. 27, 2017 USD ($)	Oct. 31, 2016 USD ($)	Dec. 23, 2014 USD ($) covenant	Jan. 17, 2014 USD ($)	Jan. 19, 2010 USD ($)	Dec. 31, 2013 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2013	Jan. 01, 2019 USD ($)	May 03, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015	Dec. 22, 2014 USD ($)
Line of Credit Facility [Line Items]
Proceeds from revolving facility								$ 12,500,000	$ 0
Amount of line of credit outstanding								$ 13,677,000					$ 0
SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Credit facility, term						4 years
Revolving credit facility, unused capacity, commitment fee percentage										0.50%
Line of Credit [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Revolving credit facility, unused capacity, commitment fee percentage								0.25%
Interest rate during period								3.50%
Sun Trust Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Proceeds from revolving facility		$ 10,000,000	$ 3,600,000
Amount of line of credit outstanding								$ 13,600,000
Line of credit remaining borrowing capacity								$ 21,400,000
Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity of credit facility	$ 35,000,000.0			$ 20,000,000.0	$ 25,000,000	$ 15,000,000.0						$ 20,000,000.0			$ 25,000,000
Debt instrument, variable interest rate, term				1 month
Revolving credit facility, unused capacity, commitment fee percentage				0.25%	0.50%
Long-term debt, percentage bearing fixed interest, percentage rate					1.75%
Number of debt covenants | covenant				2
Debt instrument, term of debt covenants to apply				30 days
Sun Trust Term Loan [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Debt instrument, face amount						15,000,000.0
Debt instrument, periodic payment, principal						$ 800,000
Debt instrument, financial principal payment							$ 3,000,000
Long-term debt, weighted average interest rate													0.25%	0.25%
London Interbank Offered Rate (LIBOR) [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Debt instrument, variable interest rate, term										1 month
London Interbank Offered Rate (LIBOR) [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable margin (percent)				1.75%
Minimum [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable margin (percent)										2.25%
Maximum [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable margin (percent)										3.50%
Scenario, Forecast [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity of credit facility											$ 30,000,000.0
Pricing Level One | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Leverage Ratio	1.25
Applicable Percentage For Commitment Fee	0.25%
Pricing Level One | London Interbank Offered Rate (LIBOR) [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable margin (percent)	2.25%
Pricing Level One | Base Rate [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable margin (percent)	1.25%
Pricing Level Two | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable Percentage For Commitment Fee	0.375%
Pricing Level Two | London Interbank Offered Rate (LIBOR) [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable margin (percent)	2.50%
Pricing Level Two | Base Rate [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable margin (percent)	1.50%
Pricing Level Two | Minimum [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Leverage Ratio	1.25
Pricing Level Two | Maximum [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Leverage Ratio	1.75
Pricing Level Three | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Leverage Ratio	1.75
Applicable Percentage For Commitment Fee	0.375%
Pricing Level Three | London Interbank Offered Rate (LIBOR) [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable margin (percent)	2.75%
Pricing Level Three | Base Rate [Member] | Sun Trust Revolving Credit Facility [Member] | SunTrust Bank [Member]
Line of Credit Facility [Line Items]
Applicable margin (percent)	1.75%