Stock-based Compensation Plans - TSR - PSUs Activities (Detail) - Performance Based TSR - PSUs	9 Months Ended
	Sep. 30, 2020 $ / shares shares
Summary of Performance Share Unit Awards outstanding, Number of Units
Outstanding, Beginning Balance | shares	993,452
Granted | shares	610,155	[1]
Vested | shares	(278,184)	[2]
Forfeited | shares	(75,899)
Outstanding, Ending Balance | shares	1,249,524
Summary of Performance Share Unit Awards outstanding, Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance, weighted average grant date fair value | $ / shares	$ 19.00
Granted, weighted average grant date fair value | $ / shares	3.85	[1]
Vested, weighted average grant date fair value | $ / shares	26.12	[2]
Forfeited, weighted average grant date fair value | $ / shares	26.66
Outstanding, Ending Balance, weighted average grant date fair value | $ / shares	$ 9.55

[1] These amounts reflect the number of performance units granted. The actual payout of shares may be between zero and 200% of the performance units granted depending on the total shareholder return ranking compared to our peer companies at the vesting date.

[2] Includes TSR-PSUs awards issued related to the 2017 performance period where the return on our common stock was in the 60^th percentile for the March 2017 grant and the 80^th percentile for the May 2017 grant. The remaining 2017 awards are considered to be forfeited.