Sale and Leaseback Transactions - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Sale Leaseback Transaction [Line Items]
Deferred gain on sale of property	$ 32.7	$ 35.6
Deferred Gains [Member]
Sale Leaseback Transaction [Line Items]
Deferred gain on sale of property	$ 29.5	$ 32.4

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_SaleLeasebackTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration