Summary of Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Basic net income (loss)	$ (1,477)	$ 11,897	$ 1,609	$ 130,049
Effect of diluted securities		1,201		3,600
Diluted net income (loss)	$ (1,477)	$ 13,098	$ 1,609	$ 133,649
Denominator:
Basic weighted average shares outstanding (in shares)	22,504	22,416	22,487	22,403
Effect of diluted securities (in shares)		4,238	187	4,203
Diluted weighted average shares outstanding (in shares)	22,504	26,654	22,674	26,606
Basic earnings (loss) per share (in dollars per share)	$ (0.07)	$ 0.53	$ 0.07	$ 5.81
Diluted earnings (loss) per share (in dollars per share)	$ (0.07)	$ 0.49	$ 0.07	$ 5.02