Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Subsequent Events (Detail) - $ / shares			3 Months Ended	12 Months Ended
Subsequent Events (Detail) - $ / shares	Feb. 07, 2018	Feb. 01, 2017	Dec. 31, 2017	Dec. 31, 2017
Subsequent Event [Line Items]
Cash dividends declared (in dollars per share)		$ 0.25	$ 0.25	$ 1.00
Subsequent event
Subsequent Event [Line Items]
Cash dividends declared (in dollars per share)	$ 0.25