Equity Transactions and Share-based Compensation (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 01, 2019	Mar. 31, 2020	Mar. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued for restricted stock units (in shares)		163,000	168,000
Acceleration compensation			$ 1.8
The 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Evergreen option provision, equity increase		4.00%
Additional shares authorized (in shares)	2,500,000
Number of shares reserved for future issuance (in shares)		1,700,000
Shares issued pursuant to the exercise of stock options (in shares)		0	8,000
The 2013 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Evergreen option provision, equity increase		1.00%
Additional shares authorized (in shares)	422,535
Number of shares reserved for future issuance (in shares)		2,600,000
Number of shares authorized to be granted (in shares)		3,500,000
Number of shares reserved for issuance, annual increase (in shares)		422,535
Participation term		2 years
Percentage of pay that employee can contribute, maximum		15.00%
Discounted purchase price from market price, offering date		15.00%
Discounted purchase price from market price, purchase date		15.00%
Purchase interval		6 months
Shares issued pursuant to employee stock purchase plan (in shares)		177,000	113,000