Preferred and Common Stock - Schedule of Activity for Stock Options and Stock Units (Detail)	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of options, Outstanding end of year	2,036,625
Stock Units [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of units, Outstanding beginning of year	2,127,611
Number of units, Granted	2,016,468
Number of units, Exercised	0
Number of units, Converted	(447,862)
Number of units, Expired or forfeited	(230,785)
Number of units, Performance share adjustment	(174,753)
Number of units, Outstanding end of year	3,290,679
Weighted average FMV per unit, Outstanding beginning of year | $ / shares	$ 36.85
Stock granted, Fair value | $ / shares	15.71
Weighted average FMV per unit, Exercised | $ / shares	0
Weighted average FMV per unit, Converted | $ / shares	37.73
Weighted average FMV per unit, Expired or forfeited | $ / shares	26.59
Weighted average FMV per unit, Performance share adjustment | $ / shares	63.21
Weighted average FMV per unit, Outstanding, end of year | $ / shares	$ 24.19
Stock Options [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of options, Outstanding beginning of year	2,246,563
Number of options, Granted	340,400
Number of options, Exercised	(55,136)
Number of options, Converted	0
Number of options, Expired or forfeited	(495,202)
Number of options, Performance share adjustment	0
Number of options, Outstanding end of year	2,036,625
Weighted average exercise price, Outstanding beginning of year | $ / shares	$ 28.38
Weighted average exercise price, granted | $ / shares	16.29
Weighted average exercise price, exercised | $ / shares	16.26
Weighted average exercise price, Converted | $ / shares	0
Weighted average exercise price, Expired or forfeited | $ / shares	27.70
Weighted average exercise price, Performance share adjustment | $ / shares	0
Weighted average exercise price Outstanding, end of year | $ / shares	$ 26.85