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Stock-Based Compensation - Assumptions For Performance Stock Units (Details) - Performance stock units
9 Months Ended
Sep. 30, 2019
simulation
$ / shares
Sep. 30, 2018
simulation
$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Vesting period 3 years  
Weighted average grant-date fair value (in dollars per share) | $ / shares $ 6.68 $ 22.35
Number of simulations | simulation 1,000,000 1,000,000
Expected stock volatility 52.30% 40.20%
Dividend yield 0.00% 0.00%
Risk-free interest rate 1.80% 2.80%