Long-Term Debt - Additional Information (Detail)					9 Months Ended		12 Months Ended
	Nov. 07, 2019 USD ($)	May 27, 2019 USD ($)	Oct. 31, 2018	Jan. 05, 2018 USD ($)	Sep. 30, 2019 USD ($) Swap	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Long-term debt					$ 1,561,760,000		$ 1,553,389,000
Outstanding letters of credit					$ 20,400,000
Interest Rate Swaps [Member]
Debt Instrument [Line Items]
Number of interest rate swaps held | Swap					5
Notional amount of interest rate swap					$ 1,000,000,000.0
Maturity of interest rate swap					May 14, 2020
Weighted average fixed interest rate					2.45%
Variable rate of interest					0.75%
Variable rate of interest, description					variable rate of interest based upon the greater of 0.75% or the BBA LIBOR
Share Repurchase Program [Member]
Debt Instrument [Line Items]
Stock repurchases under Share Repurchase Program		$ 150,000,000.0					158,000,000.0
Privately Negotiated Transaction [Member] | Share Repurchase Program [Member]
Debt Instrument [Line Items]
Stock repurchases under Share Repurchase Program					$ 150,000,000.0
Senior Secured Credit Facilities [Member]
Debt Instrument [Line Items]
Cash paid for interest				$ 5,100,000	61,200,000	$ 61,800,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Long-term debt					50,000,000		30,000,000
Senior secured revolving					210,000,000.0
Amount available for borrowing					$ 139,600,000
Revolving Credit Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Repayment of revolving credit facility	$ 10,000,000.0
Restrictive Covenants [Member] | Senior Secured Credit Facilities [Member]
Debt Instrument [Line Items]
First lien secured net leverage ratio			625.00%
Restrictive covenants, description			The Amended Credit Agreement removed all previous financial covenants on the Term B-5 Loans. The Revolving Credit Facility requires that SEA comply with a springing maximum first lien secured leverage ratio of 6.25x to be tested as of the last day of any fiscal quarter, solely to the extent that on such date the aggregate amount of funded loans and letters of credit (excluding undrawn letters of credit in an amount not to exceed $30.0 million and cash collateralized letters of credit) under the Revolving Credit Facility exceeds an amount equal to 35% of the then outstanding commitments under the Revolving Credit Facility. As of September 30, 2019, SEA was in compliance with all covenants contained in the documents governing the Senior Secured Credit Facilities.		The Senior Secured Credit Facilities permit restricted payments in an aggregate amount per annum equal to the sum of (A) $25.0 million plus (B) an amount, if any, equal to (1) if the total net leverage ratio on a pro forma basis after giving effect to the payment of any such restricted payment, is no greater than 3.50 to 1.00, an unlimited amount, (2) if the total net leverage ratio on a pro forma basis after giving effect to the payment of any such restricted payment is no greater than 4.00 to 1.00 and greater than 3.50 to 1.00, the greater of (a) $95.0 million and (b) 7.50% of Market Capitalization (as defined in the Senior Secured Credit Facilities), (3) if the total net leverage ratio on a pro forma basis after giving effect to the payment of any such restricted payment is no greater than 4.50 to 1.00 and greater than 4.00 to 1.00, $95.0 million and (4) if the total net leverage ratio on a pro forma basis after giving effect to the payment of any such restricted payment is no greater than 5.00 to 1.00 and greater than 4.50 to 1.00, $65.0 million.
Percentage of Market Capitalization on restricted payment					7.50%
First lien secured net leverage ratio					350.00%
Total net leverage ratio, as calculated					334.00%
Restrictive Covenants [Member] | Senior Secured Credit Facilities [Member] | Maximum [Member]
Debt Instrument [Line Items]
Excludable letters of credit under maximum required first lien secured leverage ratio					$ 30,000,000.0
Restricted payment on Senior Secured Credit Facilities, base payment					25,000,000.0
Restricted payment on Senior Secured Credit Facilities, first payment					95,000,000.0
Restricted payment on Senior Secured Credit Facilities, second payment					95,000,000.0
Restricted payment on Senior Secured Credit Facilities, third payment					$ 65,000,000.0
Total leverage ratio, one					400.00%
Total leverage ratio, two					450.00%
Total leverage ratio, three					500.00%
Restrictive Covenants [Member] | Senior Secured Credit Facilities [Member] | Minimum [Member]
Debt Instrument [Line Items]
Minimum percentage of funded loan and letters of credit for covenant to apply					35.00%
Total leverage ratio, one					350.00%
Total leverage ratio, two					400.00%
Total leverage ratio, three					450.00%
Term B-5 Loans [Member]
Debt Instrument [Line Items]
Long-term debt					$ 1,511,760,000		$ 1,523,389,000
Long-term debt, maturity date					Mar. 31, 2024
Percent of original principal amount on effective date used to calculate aggregate annual amount which will amortize in equal quarterly installments					1.015%