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Stock-based Compensation and Outstanding Awards - Summary of Status of Nonvested Shares of PSAs (Detail) - Performance Share (PSAs) Member]
12 Months Ended
Dec. 31, 2018
$ / shares
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]  
Nonvested shares, beginning balance | shares 317,000
Shares, Granted | shares 202,000
Shares, Vested | shares (44,000)
Shares, Forfeited | shares (62,000)
Nonvested shares, ending balance | shares 413,000
Weighted average grant date fair value, Nonvested beginning balance | $ / shares $ 19.86
Weighted average grant date fair value, Granted | $ / shares 11.81
Weighted average grant date fair value, Vested | $ / shares 22.44
Weighted average grant date fair value, Forfeited | $ / shares 23.25
Weighted average grant date fair value, Nonvested ending balance | $ / shares $ 15.13