Preferred and Common Stock - Schedule of Activity for Stock Options and Stock Units (Parenthetical) (Detail)	12 Months Ended
Dec. 31, 2018 shares
Stock Units [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Number of shares withheld to meet statutory tax requirements	109,239

For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

No definition available.

Name:	us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration