Debt (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended	25 Months Ended
	Sep. 30, 2017	Aug. 08, 2017	Jun. 30, 2016	Nov. 30, 2015	Oct. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Sep. 30, 2017	Aug. 14, 2017	Sep. 30, 2015
Debt Instrument [Line Items]
Common stock, shares issued	53,708,000					53,708,000		53,708,000		52,665,000	53,708,000
Interest expense						$ 1,477	$ 146	$ 1,878	$ 383
Amortization of debt discount								51
Debt discount	$ 600					600		600			$ 600
2017 Term Loan, net carrying amount	73,202					73,202		73,202			73,202
Line Of Credit-UBS
Debt Instrument [Line Items]
Maximum borrowing capacity													$ 50,000
Borrowings			$ 8,000	$ 10,000	$ 32,000
Repayments			$ 1,000
Outstanding balance	50,100			$ 42,000		50,100		50,100		$ 49,000	50,100
Accrued interest								700		$ 600	1,100
Interest paid								$ 200
Line Of Credit-UBS | 30-day LIBOR
Debt Instrument [Line Items]
Spread on interest rate (as a percent)								0.65%
2017 Term Loan
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 100,000
Available borrowing capacity		75,000
Remaining borrowing capacity		$ 25,000
Repayments	0
Additional interest in the event of default (as a percent)		3.00%
Debt instrument, term		84 months
Common stock, shares issued												300,000
Debt instrument, fee amount		$ 2,400
Stock price		$ 8.16
Accrued interest						1,100
2017 Term Loan | Minimum
Debt Instrument [Line Items]
Prepayment premium (as a percent)		2.50%
2017 Term Loan | Maximum
Debt Instrument [Line Items]
Prepayment premium (as a percent)		12.50%
2017 Term Loan | Base Rate
Debt Instrument [Line Items]
Spread on interest rate (as a percent)		8.75%
Base interest rate (as a percent)		1.00%
2017 Term Loan | Direct reduction from outstanding debt balance
Debt Instrument [Line Items]
Debt instrument, fee amount	$ 1,800	$ 1,800				$ 1,800		$ 1,800			$ 1,800