Stock-Based Compensation - Stock Options Outstanding and Exercisable (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Stock options
Share-Based Compensation
Shares (in shares)	379,328
Exercisable (in shares)	51,973
Exercise Price Range $3.41 - $7.05
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) | $ / shares	$ 3.41
Exercise price, upper range limit (in dollars per share) | $ / shares	$ 7.05
Exercise Price Range $3.41 - $7.05 | Stock options
Share-Based Compensation
Shares (in shares)	308,339
Exercise Price Range $16.35 - $97.50
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) | $ / shares	$ 16.35
Exercise price, upper range limit (in dollars per share) | $ / shares	$ 97.50
Exercise Price Range $16.35 - $97.50 | Stock options
Share-Based Compensation
Shares (in shares)	50,555
Exercisable (in shares)	32,060
Exercise Price Range $222.00 - $225.00
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) | $ / shares	$ 222.00
Exercise price, upper range limit (in dollars per share) | $ / shares	$ 225.00
Exercise Price Range $222.00 - $225.00 | Stock options
Share-Based Compensation
Shares (in shares)	1,931
Exercisable (in shares)	1,594
Exercise Price Range $348.00 - $597.00
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) | $ / shares	$ 348.00
Exercise price, upper range limit (in dollars per share) | $ / shares	$ 597.00
Exercise Price Range $348.00 - $597.00 | Stock options
Share-Based Compensation
Shares (in shares)	4,931
Exercisable (in shares)	4,777
Exercise Price Range $651.00 - $1,129.50
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) | $ / shares	$ 651.00
Exercise price, upper range limit (in dollars per share) | $ / shares	$ 1,129.50
Exercise Price Range $651.00 - $1,129.50 | Stock options
Share-Based Compensation
Shares (in shares)	5,636
Exercisable (in shares)	5,606
Exercise Price Range $1,992.00 - $2,268.00
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) | $ / shares	$ 1,992.00
Exercise price, upper range limit (in dollars per share) | $ / shares	$ 2,268.00
Exercise Price Range $1,992.00 - $2,268.00 | Stock options
Share-Based Compensation
Shares (in shares)	7,585
Exercisable (in shares)	7,585
Exercise Price Range $4,156.50 - $4,371.00
Share-Based Compensation
Exercise price, lower range limit (in dollars per share) | $ / shares	$ 4,156.50
Exercise price, upper range limit (in dollars per share) | $ / shares	$ 4,371.00
Exercise Price Range $4,156.50 - $4,371.00 | Stock options
Share-Based Compensation
Shares (in shares)	351
Exercisable (in shares)	351