Derivative Instruments - Additional Information (Details) € in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2019 EUR (€)	Sep. 30, 2019 CAD ($)	Dec. 31, 2018 CAD ($)
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	132,000,000
Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value		$ 2,500,000,000
Interest rate swaps | Interest expense, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net unrealized loss recognized at settlement		$ 85,000,000
Interest Rate Swaps - Period One
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value	3,500,000,000
Interest Rate Swaps - Period Two
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value	500,000,000
Cross Currency Interest Rate Contract | Fixed Income Interest Rate
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value	5,000,000,000			$ 6,754,000,000	$ 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
Derivatives designated as net investment hedges | Cross Currency Interest Rate Contract | Fixed Income Interest Rate
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value	$ 500,000,000