Share-Based Compensation - Summary of Stock Option Activity (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2019 $ / shares shares
Number of Shares Underlying Options
Outstanding at beginning of year (in shares) | shares	5,903
Granted (in shares) | shares	177
Forfeited (in shares) | shares	(420)
Expired (in shares) | shares	(192)
Outstanding at end of year (in shares) | shares	5,468
Vested and exercisable, September 30, 2019 (in shares) | shares	2,946
Vested and expected to vest, September 30. 2019 (in shares) | shares	5,266
Weighted Average Exercise Price
Outstanding at beginning of year (in dollars per share) | $ / shares	$ 13.72
Granted (in dollars per share) | $ / shares	1.31
Forfeited (in dollars per share) | $ / shares	19.59
Expired (in dollars per share) | $ / shares	26.87
Outstanding at end of year (in dollars per share) | $ / shares	12.41
Vested and exercisable, September 30, 2019 (in dollars per share) | $ / shares	20.06
Vested and expected to vest, September 30. 2019 (in dollars per share) | $ / shares	$ 12.76