Derivative Instruments - Additional Information (Details)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2018 EUR (€)	Jun. 30, 2017 CAD ($)
Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value		$ 170,000,000
Interest expense, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of pre-tax losses in AOCI expect to be reclassified into interest expense		12,300,000
Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value		$ 3,500,000,000	$ 2,500,000,000
Interest rate swaps, maturity date		Feb. 17, 2024	Apr. 26, 2018
Interest rate swaps | Interest expense, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net unrealized loss remaining in AOCI			$ 84,600,000
Cross currency interest rate contract
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value	$ 5,000,000,000
Cash received on hedge	763,500,000
Net unrealized gains as of termination date	533,400,000
Cross currency interest rate contract | Fixed income interest rate
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional value	$ 5,000,000,000				$ 6,753,500,000.0
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		€ 1,107,800,000.0
Interest Rate Swaps outstanding | Interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Type of interest rate paid on swap			fixed