Debt - Narrative (Details)			1 Months Ended								9 Months Ended			25 Months Ended	29 Months Ended	31 Months Ended	33 Months Ended	34 Months Ended	85 Months Ended	109 Months Ended
		Oct. 01, 2020	Mar. 31, 2021	Oct. 31, 2020 USD ($) $ / shares	Sep. 30, 2020 USD ($)	Aug. 31, 2020 USD ($)	Jun. 30, 2020 USD ($) $ / shares	Jun. 30, 2020 GBP (£)	Mar. 31, 2020 USD ($) board_member	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 GBP (£)	Sep. 30, 2019 USD ($)	Jun. 01, 2022	Mar. 14, 2023 day	Aug. 14, 2023 day	Mar. 14, 2023 day	Aug. 14, 2023 day	Jun. 30, 2026	Jun. 30, 2028	Sep. 30, 2021 USD ($)	Sep. 30, 2020 GBP (£)	May 31, 2020 USD ($) ship	Feb. 29, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 GBP (£)
Long-Term Debt
Loss on extinguishment of secured senior term loan											$ 41,109,000		$ 6,326,000
Debt instrument, collateral amount					$ 80,000,000						80,000,000
Proceeds allocated to paid-in-capital							$ 209,000,000.0
Debt issuance costs							33,100,000
Issuance costs allocated to paid-in capital							6,200,000
Commercial paper | £								£ 300,000,000.0				£ 300,000,000.0
Debt amortization and financial covenant holiday, amount					900,000,000						$ 900,000,000
Amortization period											4 years	4 years
Credit agency fees, percentage of outstanding loan balance											2.97%	2.97%
Long-term debt					6,200,000,000						$ 6,200,000,000
Debt covenant, monthly minimum liquidity											500,000,000.0
Finance lease obligation					31,500,000						31,500,000														$ 55,600,000
Subsequent Event
Long-Term Debt
Debt covenant, monthly minimum liquidity				$ 350,000,000.0
Revolving Credit Facility
Long-Term Debt
Increase to revolving credit facility					$ 600,000,000						$ 600,000,000
Long-term debt							11,000,000,000.0
Minimum fixed charge coverage ratio					125.00%						125.00%											125.00%
Long-term debt
Long-Term Debt
Proceeds from debt issuance							907,900,000
Scenario, Forecast
Long-Term Debt
Debt instrument, collateral amount																					$ 60,600,000
Maximum | Contract With Customer, Liability, Up-Front Payment Arrangement
Long-Term Debt
Credit agency fees, percentage of loan amount payable											2.37%	2.37%
Minimum | Contract With Customer, Liability, Up-Front Payment Arrangement
Long-Term Debt
Credit agency fees, percentage of loan amount payable											2.35%	2.35%
Commercial Paper
Long-Term Debt
Borrowings outstanding					$ 387,900,000						$ 387,900,000											£ 300,000,000.0				£ 1,400,000,000
Revolving Credit Facility
Long-Term Debt
Maximum borrowing capacity					$ 3,400,000,000						$ 3,400,000,000
Unsecured term loans | Maximum
Long-Term Debt
Interest rate					5.41%						5.41%											5.41%
Unsecured term loans | Minimum
Long-Term Debt
Interest rate					2.53%						2.53%											2.53%
Secured senior notes | Maximum
Long-Term Debt
Interest rate					11.50%						11.50%											11.50%
Secured senior notes | Minimum
Long-Term Debt
Interest rate					7.25%						7.25%											7.25%
Unsecured senior notes | Maximum
Long-Term Debt
Interest rate					9.13%						9.13%											9.13%
Unsecured senior notes | Minimum
Long-Term Debt
Interest rate					2.65%						2.65%											2.65%
Convertible notes
Long-Term Debt
Interest rate	[1]				4.25%						4.25%											4.25%
Debt instrument, face amount					$ 1,150,000,000		$ 1,150,000,000				$ 1,150,000,000
Unsecured Revolving Credit Facility Due 2024 | Revolving Credit Facility
Long-Term Debt
Maximum borrowing capacity					1,900,000,000						1,900,000,000													$ 1,700,000,000
Increase to revolving credit facility									$ 200,000,000
Unsecured Revolving Credit Facility Due 2022 | Revolving Credit Facility
Long-Term Debt
Maximum borrowing capacity					1,500,000,000						1,500,000,000													$ 1,200,000,000
Increase to revolving credit facility									$ 400,000,000
Celebrity Apex Unsecured Term Loan | Celebrity Apex | Bpifrance Assurance Export
Long-Term Debt
Percentage guaranteed by export credit agency									100.00%
Celebrity Apex Unsecured Term Loan | Unsecured term loans
Long-Term Debt
Unsecured debt									$ 722,200,000
Debt instrument, term									12 years
Interest rate									3.23%
Senior Secured Term Loan Agreement | Secured term loan
Long-Term Debt
Increase to revolving credit facility																							$ 150,000,000
Debt instrument, term									364 days
Debt instrument, face amount									$ 2,200,000,000														2,350,000,000
Debt instrument, extension period									364 days
Extension fee percent									1.00%
Duration fee percentage									0.25%
Number of board members | board_member									2
Senior Secured Term Loan Agreement | Secured term loan | Board Member One | Director
Long-Term Debt
Related party transaction									$ 100,000,000
Senior Secured Term Loan Agreement | Secured term loan | Board Member Two | Director
Long-Term Debt
Related party transaction									$ 100,000,000
Senior Secured Notes | Secured senior notes
Long-Term Debt
Debt instrument, face amount																							$ 3,320,000,000
Percentage of equity interests pledged as collateral																							100.00%
Number of ships owned by subsidiaries | ship																							28
Senior Secured Notes | Secured senior notes | Scenario, Forecast
Long-Term Debt
Redemption price, principal of amount redeemed														100.00%
Senior Secured Notes | Secured senior notes | Maximum
Long-Term Debt
Debt instrument, collateral amount																							$ 1,660,000,000
Senior Secured Notes due 2023 | Secured senior notes
Long-Term Debt
Interest rate																							10.875%
Debt instrument, face amount																							$ 1,000,000,000.0
Senior Secured Notes due 2025 | Secured senior notes
Long-Term Debt
Interest rate																							11.50%
Debt instrument, face amount																							$ 2,320,000,000
Senior Guaranteed Notes | Unsecured senior notes
Long-Term Debt
Interest rate							9.125%
Debt instrument, face amount							$ 1,000,000,000.0
Percentage of equity interests pledged as collateral							100.00%
Convertible Notes 4.25%, Due 2023 | Convertible notes
Long-Term Debt
Interest rate							4.25%
Debt instrument, face amount							$ 1,150,000,000
Redemption price, principal of amount redeemed							100.00%	100.00%
Conversion ratio							0.0138672	0.0138672
Conversion price (in dollars per share) | $ / shares							$ 72.11
Convertible Notes 4.25%, Due 2023 | Convertible notes | Subsequent Event
Long-Term Debt
Redemption price, principal of amount redeemed		100.00%
Convertible Notes 4.25%, Due 2023 | Convertible notes | Scenario, Forecast
Long-Term Debt
Number of trading days | day															20
Consecutive trading days | day															30		10
Percentage of stock price															130.00%		98.00%
Number of days to convert debt | day																	5
Term Loan Facility, $700 Million | Line of Credit
Long-Term Debt
Maximum borrowing capacity					700,000,000	$ 700,000,000					700,000,000
Term loan facility increase limit						$ 300,000,000
Senior Convertible Notes Due 2023 | Convertible notes | Subsequent Event
Long-Term Debt
Interest rate				2.875%
Debt instrument, face amount				$ 575,000,000
Conversion ratio				0.0121212
Conversion price (in dollars per share) | $ / shares				$ 82.50
Senior Convertible Notes Due 2023 | Convertible notes | Scenario, Forecast
Long-Term Debt
Number of trading days | day																20
Consecutive trading days | day																30		10
Percentage of stock price																130.00%		98.00%
Number of days to convert debt | day																		5
Senior Notes Due 2020 | Unsecured senior notes | Subsequent Event
Long-Term Debt
Interest rate				2.65%
Term Loan Due 2023 | Unsecured term loans
Long-Term Debt
Debt instrument, face amount					$ 130,000,000.0						$ 130,000,000.0
Silver Moon Credit Agreement | Unsecured term loans
Long-Term Debt
Debt instrument, face amount										$ 300,000,000
Silver Moon Credit Agreement | Unsecured term loans | Scenario, Forecast
Long-Term Debt
Repayment advance notice																			90 days
Periodic payment, percentage of principal																				4.17%
LIBOR | Unsecured Revolving Credit Facility Due 2024 | Revolving Credit Facility
Long-Term Debt
Debt instrument, basis spread on variable rate											1.30%	1.30%
LIBOR | Unsecured Revolving Credit Facility Due 2022 | Revolving Credit Facility
Long-Term Debt
Debt instrument, basis spread on variable rate											1.30%	1.30%
LIBOR | Senior Secured Term Loan Agreement | Secured term loan
Long-Term Debt
Debt instrument, basis spread on variable rate					2.50%				2.25%
LIBOR | Senior Secured Term Loan Agreement | Secured term loan | Scenario, Forecast
Long-Term Debt
Debt instrument, basis spread on variable rate			2.75%
LIBOR | Term Loan Facility, $700 Million | Line of Credit
Long-Term Debt
Debt instrument, basis spread on variable rate						3.75%
LIBOR | Silver Moon Credit Agreement | Unsecured term loans
Long-Term Debt
Debt instrument, basis spread on variable rate										1.50%

[1] Interest rates based on outstanding loan balance as of September 30, 2020 and, for variable rate debt, include either LIBOR or EURIBOR plus the applicable margin.