Fair Value Measurements - Items Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Liability | CEC Convertible Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		$ 324
Liability | CEC Convertible Notes | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0
Liability | CEC Convertible Notes | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		324
Liability | CEC Convertible Notes | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability		0
Estimate of Fair Value Measurement | Fair Value, Recurring | Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	$ 13	21
Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	0	0
Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	13	21
Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets at fair value	0	0
Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | US Treasury and Government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	13	15
Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | US Treasury and Government | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | US Treasury and Government | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	13	15
Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | US Treasury and Government | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
Estimate of Fair Value Measurement | Fair Value, Recurring | Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Disputed claims liability	51	45
Total liabilities at fair value	1,064	391
Estimate of Fair Value Measurement | Fair Value, Recurring | Liability | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Disputed claims liability	0	0
Total liabilities at fair value	0	0
Estimate of Fair Value Measurement | Fair Value, Recurring | Liability | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Disputed claims liability	51	45
Total liabilities at fair value	1,064	391
Estimate of Fair Value Measurement | Fair Value, Recurring | Liability | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Disputed claims liability	0	0
Total liabilities at fair value	0	0
Interest Rate Swap | Estimate of Fair Value Measurement | Fair Value, Recurring | Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	69
Interest Rate Swap | Estimate of Fair Value Measurement | Fair Value, Recurring | Liability | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	0
Interest Rate Swap | Estimate of Fair Value Measurement | Fair Value, Recurring | Liability | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	69
Interest Rate Swap | Estimate of Fair Value Measurement | Fair Value, Recurring | Liability | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	0
CEC Convertible Notes | Estimate of Fair Value Measurement | Fair Value, Recurring | Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments - interest rate swaps		6
CEC Convertible Notes | Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments - interest rate swaps		0
CEC Convertible Notes | Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments - interest rate swaps		6
CEC Convertible Notes | Estimate of Fair Value Measurement | Fair Value, Recurring | Assets | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments - interest rate swaps		0
CEC Convertible Notes | Estimate of Fair Value Measurement | Fair Value, Recurring | Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	944	22
CEC Convertible Notes | Estimate of Fair Value Measurement | Fair Value, Recurring | Liability | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	0	0
CEC Convertible Notes | Estimate of Fair Value Measurement | Fair Value, Recurring | Liability | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	944	22
CEC Convertible Notes | Estimate of Fair Value Measurement | Fair Value, Recurring | Liability | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	$ 0	$ 0