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Long-term debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 10, 2020	Feb. 11, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total principal long-term debt	$ 3,940,000			$ 4,203,000
Debt issuance costs	(40,175)			(26,873)
Unamortized premiums and discounts, net	6,371			3,118
Total long-term debt	3,906,196			4,179,245
Unsecured floating rate term loan due quarterly through June 2020
Debt Instrument [Line Items]
Total principal long-term debt	0			20,000
Unsecured floating rate term loan due quarterly through September 2020
Debt Instrument [Line Items]
Total principal long-term debt	0			105,000
Unsecured notes bearing fixed rate interest at 5.125% due July 2020 \| Senior Notes
Debt Instrument [Line Items]
Total principal long-term debt	$ 0			$ 310,000
Stated interest rate (as a percent)	5.125%		5.125%	5.125%
Unsecured notes bearing fixed rate interest at 4.875% due September 2021 \| Senior Notes
Debt Instrument [Line Items]
Total principal long-term debt	$ 350,000			$ 350,000
Stated interest rate (as a percent)	0.04875%			0.04875%
Unsecured notes bearing fixed rate interest at 6.375% due October 2023 \| Senior Notes
Debt Instrument [Line Items]
Total principal long-term debt	$ 0			$ 650,000
Stated interest rate (as a percent)	0.06375%		6.375%	0.06375%
Borrowings under revolving credit agreement expiring August 2024
Debt Instrument [Line Items]
Total principal long-term debt	$ 175,000			$ 903,000
Unsecured notes bearing fixed rate interest at 5.500% due September 2024 \| Senior Notes
Debt Instrument [Line Items]
Total principal long-term debt	$ 325,000			$ 325,000
Stated interest rate (as a percent)	0.055%			0.055%
Unsecured notes bearing fixed rate interest at 4.750% due March 2026 \| Senior Notes
Debt Instrument [Line Items]
Total principal long-term debt	$ 550,000			$ 0
Stated interest rate (as a percent)	0.0475%	4.75%		0.0475%
Unsecured notes bearing fixed rate interest at 7.75% due June 2027 \| Senior Notes
Debt Instrument [Line Items]
Total principal long-term debt	$ 200,000			$ 200,000
Stated interest rate (as a percent)	0.0775%			0.0775%
Unsecured notes bearing fixed rate interest at 7.25% due September 2027 \| Senior Notes
Debt Instrument [Line Items]
Total principal long-term debt	$ 240,000			$ 240,000
Stated interest rate (as a percent)	0.0725%			0.0725%
Unsecured notes bearing fixed rate interest at 4.625% due March 2028 \| Senior Notes
Debt Instrument [Line Items]
Total principal long-term debt	$ 1,000,000			$ 0
Stated interest rate (as a percent)	0.04625%			0.04625%
Unsecured notes bearing fixed rate interest at 5.00% due September 2029 \| Senior Notes
Debt Instrument [Line Items]
Total principal long-term debt	$ 1,100,000			$ 1,100,000
Stated interest rate (as a percent)	0.05%			0.05%