Future Minimum Lease Payments under Operating and Capital Leases (Parenthetical) (Details) $ in Millions	Dec. 31, 2017 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Capital lease payments interest included in payment	$ 2.7

Amount necessary to reduce net minimum lease payments to present value for capital leases.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84164817&loc=d3e45280-112737

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsInterestIncludedInPayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant