Preferred and Common Stock - Schedule of Activity for Stock Options and Stock Units (Detail)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of options, Exercised	(1,298,021)
Number of options, Outstanding end of year	1,959,927
Weighted average exercise price Outstanding, end of year | $ / shares	$ 21.44
Stock Units [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of units, Outstanding beginning of year	2,301,332
Number of units, Granted	635,477
Number of units, Exercised	0
Number of units, Converted	(505,930)
Number of units, Expired or forfeited	(40,941)
Number of units, Performance share adjustment	(84,793)
Number of units, Outstanding end of year	2,305,145
Weighted average FMV per unit, Outstanding beginning of year | $ / shares	$ 26.93
Stock granted, Fair value | $ / shares	52.81
Weighted average FMV per unit, Exercised | $ / shares	0
Weighted average FMV per unit, Converted | $ / shares	34.55
Weighted average FMV per unit, Expired or forfeited | $ / shares	31.73
Weighted average FMV per unit, Performance share adjustment | $ / shares	15.09
Weighted average FMV per unit, Outstanding, end of year | $ / shares	$ 32.75
Stock Options [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of options, Outstanding beginning of year	2,687,107
Number of options, Granted	189,455
Number of options, Exercised	(896,645)
Number of options, Converted	0
Number of options, Expired or forfeited	(19,990)
Number of options, Performance share adjustment	0
Number of options, Outstanding end of year	1,959,927
Weighted average exercise price, Outstanding beginning of year | $ / shares	$ 25.48
Weighted average exercise price, granted | $ / shares	53.30
Weighted average exercise price, exercised | $ / shares	25.06
Weighted average exercise price, Converted | $ / shares	0
Weighted average exercise price, Expired or forfeited | $ / shares	20.51
Weighted average exercise price, Performance share adjustment | $ / shares	0
Weighted average exercise price Outstanding, end of year | $ / shares	$ 28.41