Debt - Narrative (Details) - USD ($)						1 Months Ended			12 Months Ended
	Dec. 21, 2018	Dec. 13, 2018	Jul. 16, 2018	Jun. 01, 2018	Apr. 27, 2018	Feb. 28, 2019	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 22, 2014	Dec. 16, 2014
Debt Instrument [Line Items]
Partial extinguishment of equity component of Convertible 3.75% Senior Notes									$ (10,522,000)
Proceeds from 2021 revolver									$ 15,000,000	$ 0	$ 0
Line of Credit
Debt Instrument [Line Items]
Proceeds from 2021 revolver								$ 52,800,000
Covenant, revenue required to attain		$ 125,000,000.0
Convertible debt
Debt Instrument [Line Items]
Stated interest rate								3.75%	3.75%
Initial Issuance | Convertible debt
Debt Instrument [Line Items]
Face amount of the Notes													$ 125,000,000.0
Additional Principal | Convertible debt
Debt Instrument [Line Items]
Face amount of the Notes												$ 18,750,000
Senior Notes, due December 2019
Debt Instrument [Line Items]
Stated interest rate								3.75%	3.75%
Loss on debt extinguishment								$ 1,700,000	$ 2,500,000
Partial extinguishment of equity component of Convertible 3.75% Senior Notes								(2,900,000)
Senior Notes, due December 2019 | Convertible debt
Debt Instrument [Line Items]
Face amount of the Notes								$ 75,090,000	$ 75,090,000
Stated interest rate								4.75%	4.75%
Debt transfer amount					$ 75,100,000
Partial extinguishment of equity component of Convertible 3.75% Senior Notes									$ (7,600,000)
Transaction costs								$ 300,000
Senior Notes, due December 2019 | Convertible debt | Subsequent Event
Debt Instrument [Line Items]
Repayment of term loan						$ 2,200,000	$ 500,000
Senior Notes, Due 2023 | Convertible debt
Debt Instrument [Line Items]
Stated interest rate					4.75%
Conversion price (in dollars per share)					$ 224.71
Settlement conversion price (dollars per share)					$ 280.90
Debt issuance costs					$ 1,600,000
Unamortized discount					$ 19,000,000.0
Interest rate, effective percentage					11.90%
Deferred financing costs					$ 1,600,000
Term Loan, due 2021
Debt Instrument [Line Items]
Face amount of the Notes				$ 25,000,000.0
Debt issuance costs				500,000
Unamortized discount				$ 400,000
Interest rate, effective percentage				12.78%
Loss on debt extinguishment									1,300,000
Covenant, minimum cash balance				$ 5,000,000.0
Proceeds from 2021 revolver			$ 10,000,000.0	15,000,000.0
Deferred financing costs				$ 500,000
Transaction costs								500,000
Interest rate floor				2.00%
Repayment of term loan								25,600,000
Repayments of long-term debt, interest								100,000
Term Loan, due 2021 | LIBOR
Debt Instrument [Line Items]
Applicable margin				9.00%
Revolving Credit Facility | Line of Credit
Debt Instrument [Line Items]
Face amount of the Notes								$ 15,000,000	$ 15,000,000
Debt issuance costs		300,000
Unamortized discount		500,000
Line of credit maximum borrowing capacity		25,000,000.0
Proceeds from 2021 revolver		15,000,000.0
Deferred financing costs		$ 300,000
Effective interest rate								9.30%	9.30%
Revolving Credit Facility | Line of Credit | Subsequent Event
Debt Instrument [Line Items]
Proceeds from 2021 revolver							5,000,000.0
Remaining borrowing capacity							$ 10,000,000.0
Revolving Credit Facility | LIBOR | Line of Credit
Debt Instrument [Line Items]
Applicable margin		3.75%
Revolving Credit Facility | Base Rate | Line of Credit
Debt Instrument [Line Items]
Applicable margin		2.75%
Term Loan | Line of Credit
Debt Instrument [Line Items]
Debt issuance costs		$ 800,000
Unamortized discount		1,800,000
Interest rate, effective percentage								12.40%	12.40%
Deferred financing costs		$ 800,000
Unused borrowing capacity, fee percentage		1.00%
Term Loan | LIBOR | Line of Credit
Debt Instrument [Line Items]
Applicable margin		8.75%
Term Loan | Base Rate | Line of Credit
Debt Instrument [Line Items]
Applicable margin		7.75%
Term Loan | Initial Term Loan | Line of Credit
Debt Instrument [Line Items]
Face amount of the Notes		$ 50,000,000.0						$ 70,000,000	$ 70,000,000
Term Loan | Delayed Draw Term Loan A
Debt Instrument [Line Items]
Debt issuance costs		500,000
Deferred financing costs		500,000
Amount drawn on term loan	$ 20,000,000.0
Term Loan | Delayed Draw Term Loan A | Line of Credit
Debt Instrument [Line Items]
Face amount of the Notes		30,000,000.0
Amount still available on loan agreements								10,000,000.0	10,000,000.0
Term Loan | Delayed Draw Term Loan B | Line of Credit
Debt Instrument [Line Items]
Face amount of the Notes		$ 15,000,000.0
Amount still available on loan agreements								$ 15,000,000.0	$ 15,000,000.0