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Stock-Based Compensation - Schedule of Restricted Stock Activity (Details) - Restricted Stock Awards - $ / shares
1 Months Ended 12 Months Ended
Jul. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Shares          
Outstanding, beginning balance (in shares)   104,340 130,244 154,251 162,993
Granted (in shares) 379,472 437,472 750 1,000 23,000
Forfeited (in shares)   (29,144) (4,668) (800) (12,000)
Vested (in shares)   (16,395) (21,986) (24,207) (19,742)
Outstanding, ending balance (in shares)   496,273 104,340 130,244 154,251
Weighted-Average Grant Date Fair Value          
Outstanding, beginning balance (in dollars per share)   $ 41.61 $ 41.77 $ 42.11 $ 39.29
Granted (in dollars per share)   8.13 18.50 28.48 71.47
Forfeited (in dollars per share)   38.33 36.00 65.51 60.44
Vested (in dollars per share)   44.19 42.96 42.63 41.89
Outstanding, ending balance (in dollars per share)   $ 12.20 $ 41.61 $ 41.77 $ 42.11