Share-Based Compensation - Restricted Stock Table (Details) - Restricted stock [Member] shares in Thousands	3 Months Ended
	Mar. 31, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested restricted stock, beginning balance | shares	13,178
Granted (in shares) | shares	2,805
Vested (in shares) | shares	(4,651)
Forfeited (in shares) | shares	(465)
Unvested restricted stock, beginning balance | shares	10,867
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted average grant date fair value, unvested restricted stock, beginning balance (in dollars per share) | $ / shares	$ 6.37
Weighted average grant date fair value, granted (in dollars per share) | $ / shares	3.02
Weighted average grant date fair value, vested (in dollars per share) | $ / shares	7.64
Weighted average grant date fair value, forfeited (in dollars per share) | $ / shares	6.24
Weighted average grant date fair value, unvested restricted stock, ending balance (in dollars per share) | $ / shares	$ 4.97