Summary of Significant Accounting Policies (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended
	Jul. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Held-to-maturity Securities		$ 15,900,000		$ 14,400,000
Notes, Loans and Financing Receivable, Net, Noncurrent		9,000,000		4,000,000
Long-term Debt		1,440,000,000		1,440,500,000
Land Not Used In Operations		27,200,000
Statements of Operations
Gaming taxes		81,100,000	76,600,000
Pre-opening and development costs		7,561,000	2,758,000
Land and land improvements		297,100,000		291,900,000
Buildings, riverboats and improvements		1,538,300,000		1,539,300,000
Furniture, fixtures and equipment		531,100,000		528,000,000
Construction in progress		84,200,000		47,900,000
Land, buildings, vessels and equipment, gross		2,450,700,000		2,407,100,000
Less: accumulated depreciation		(732,100,000)		(711,100,000)
Stock Repurchase Program, Authorized Amount	100,000,000
Treasury Stock, Shares, Acquired		4.4
Purchase of treasury shares		51,000,000
Prior Period Reclassification Adjustment		2,700,000
Customer Loyalty Program Liability		13,100,000		11,500,000
Pinnacle Retama Partners
Business Acquisition, Percentage of Voting Interests Acquired		75.50%
Statements of Operations
Goodwill, Acquired During Period		3,300,000
Acquired Indefinite-lived Intangible Asset, Amount		5,000,000
Other
Statements of Operations
Pre-opening and development costs		800,000	2,800,000
Stock Options
Statements of Operations
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		1.2	0.4
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Recurring [Member]
Deferred Compensation		800,000		1,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Fair Value, Measurements, Nonrecurring [Member]
Held-to-maturity Debt Securities		31,200,000
Promissory Notes		15,900,000		4,000,000
Long-term Debt,Fair Value		1,534,000,000		1,532,100,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Deferred Compensation		800,000		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Held-to-maturity Debt Securities		0		0
Promissory Notes		0		0
Long-term Debt,Fair Value		0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Deferred Compensation		0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Held-to-maturity Debt Securities		31,200,000		14,400,000
Promissory Notes		15,900,000		4,000,000
Long-term Debt,Fair Value		1,534,000,000		1,532,100,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Deferred Compensation		0		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Held-to-maturity Debt Securities		0		0
Promissory Notes		0		0
Long-term Debt,Fair Value		0		0
Ameristar
Business Acquisition, Share Price		$ 26.50
Line of Credit Facility, Maximum Borrowing Capacity		1,040,000,000
Debt Instrument, Consent Fee		19.00
Debt Instrument, Face Amount		1,000
Business Acquisition, Percentage of Bondholders Consent Fees		50.00%
Business Acquisition, Funds Required		1,000,000,000
Business Acquisition - Goodwill
Purchase price		2,800,000,000
Statements of Operations
Pre-opening and development costs		6,800,000	0
Loss on Contract Termination for Default		85,000,000
Senior Notes Due 2021 | Ameristar
Debt Instrument, Interest Rate, Stated Percentage		7.50%
Ameristar
Other Long-term Debt		$ 9,800,000