Number of shares issued for each share of convertible preferred stock that is converted.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(27))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Name:	us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Subsequent Events - Additional Information (Detail) - $ / shares		12 Months Ended
	Dec. 17, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 02, 2020	Jan. 01, 2020
Subsequent Event [Line Items]
Dividend declared common share, per share		$ 0.43	$ 0.56	$ 0.60
Series B Preferred Stock
Subsequent Event [Line Items]
Conversion of preferred stock, conversion rate (in shares)		5.5379
Dividend declared common share, per share	$ 0.09
Subsequent Event \| Series B Preferred Stock
Subsequent Event [Line Items]
Conversion of preferred stock, conversion rate (in shares)					5.5992	5.5379