Uniwheels Noncontrolling Redeemable Equity - Additional Information (Detail) $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Redeemable Noncontrolling Interest [Line Items]
Accrued annual dividend to noncontrolling interest	$ 0.6
Domination and Profit Loss Transfer Agreement [Member]
Redeemable Noncontrolling Interest [Line Items]
Noncontrolling interests with carrying value reclassified from stockholders' equity to mezzanine equity	$ 51.9

Dividends paid to preferred stock holders that is redeemable solely at the option of the issuer.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=96947427&loc=d3e1377-109256

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644

Reference 3: 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

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