Commitments and Contingencies (Gain Contingency) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2008 State of Nevada Department of Taxation Minimum Reduction in State Use Taxes	Dec. 31, 2008 State of Nevada Department of Taxation Maximum Reduction in State Use Taxes	Sep. 30, 2013 Subsidiary, Borgata Real Estate Taxes [Member]
Gain Contingencies [Line Items]
Estimated refund claimed	$ 19.1	$ 21.6	$ 48.0
Gain Contingency, Unrecorded Amount, Interest			$ 9.0

The amount or range of possible amounts of gain that could be realized upon the resolution of a contingency.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 17

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 30

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6397426&loc=d3e17499-108355

Name:	us-gaap_GainContingencyUnrecordedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant