Derivative Instruments - Additional Information (Details) € in Millions, $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2019 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2019 CAD ($)	Jun. 30, 2019 EUR (€)	Dec. 31, 2018 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of pre-tax losses in AOCI expect to be reclassified into interest expense	$ 12,000,000
Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value	130,000,000
Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value		$ 2,500,000,000			$ 3,500,000,000
Interest rate swaps | Interest expense, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net unrealized loss recognized at settlement		$ 85,000,000
Cross currency interest rate contract | Fixed income interest rate
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value	5,000,000,000		$ 6,754		$ 400,000,000
Cross currency interest rate contract | Fixed income interest rate | Hedge Funds
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value	$ 1,200,000,000			€ 1,108