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Stock-based Compensation Plans - Valuation Assumptions for Grant Date Fair Value of Performance Awards (Detail) - Market-based TSR - $ / shares
9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Risk-free interest rate 1.49% 0.94%
Expected annual volatility 44.00% 49.00%
Weighted average grant date fair value per unit $ 26.26 [1] $ 36.64
[1] Amounts granted reflect the number of performance units granted; however, the actual payout of shares will be between zero and 150% of the performance units granted depending on the total shareholder return ranking compared to the peer companies at the end of the three-year performance period