Financial Instruments and Risk Concentration (Details)	Feb. 24, 2020	Jan. 31, 2020	Dec. 31, 2019
5.00% senior notes due September 2020
Debt Instrument, Interest Rate, Stated Percentage	5.00%		5.00%
4.625% senior notes due September 2021
Debt Instrument, Interest Rate, Stated Percentage		4.625%	4.625%
Senior Notes 5.50 Percentage Due Two Zero Two Three [Member]
Debt Instrument, Interest Rate, Stated Percentage			5.50%
5.10% senior notes due September 2023
Debt Instrument, Interest Rate, Stated Percentage	5.10%	5.10%	5.10%
5.75% senior notes due February 2025
Debt Instrument, Interest Rate, Stated Percentage			5.75%