Stock-based Compensation Plans - TSR - PSUs Activities (Detail) - Performance Based TSR - PSUs	6 Months Ended
	Jun. 30, 2021 $ / shares shares
Summary of Performance Share Unit Awards outstanding, Number of Units
Outstanding, Beginning Balance | shares	1,249,524
Granted | shares	223,687	[1]
Vested and issued | shares	(325,217)	[2]
Forfeited | shares	0
Outstanding, Ending Balance | shares	1,147,994
Summary of Performance Share Unit Awards outstanding, Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance, weighted average grant date fair value | $ / shares	$ 9.55
Granted, weighted average grant date fair value | $ / shares	12.58
Vested and issued, weighted average grant date fair value | $ / shares	18.51
Forfeited, weighted average grant date fair value | $ / shares	0
Outstanding, Ending Balance, weighted average grant date fair value | $ / shares	$ 7.60

[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 2018 performance period where the return on our common stock was was negative and therefore, the performance multiple and actual payout was reduced to 100%.