Summary of Significant Accounting Policies - Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of Significant Accounting Policies
Weighted average shares, issuance of restricted stock									83,076	61,101	67,274
Nonvested restricted stock shares excluded from total weighted average shares	108,670				332,103				108,670	332,103	127,078
Numerator:
Basic net income (loss)									$ 147,107	$ 11,950	$ (1,932)
Effect of diluted securities									2,969
Diluted net income (loss)									$ 150,076	$ 11,950	$ (1,932)
Denominator:
Basic weighted average shares outstanding (in shares)									22,346,000	22,010,000	21,945,000
Effect of diluted securities (in shares)									4,163,000	120,000
Diluted weighted average shares outstanding (in shares)									26,509,000	22,130,000	21,945,000
Basic earnings (loss) per share (in dollars per share)	$ 0.77	$ 0.53	$ 5.24	$ 0.04	$ 0.72	$ 0.25	$ (0.20)	$ (0.23)	$ 6.58	$ 0.54	$ (0.09)
Diluted earnings (loss) per share (in dollars per share)	$ 0.68	$ 0.49	$ 4.45	$ 0.04	$ 0.65	$ 0.25	$ (0.20)	$ (0.23)	$ 5.66	$ 0.54	$ (0.09)