Share Repurchase Programs and Dividends - Dividends (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Equity [Abstract]
Cash dividends declared (in dollars per share)	$ 0.1	$ 0.1
Payments of dividends	$ 48

Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration