Derivative Instruments - Additional Information (Detail) CAD in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2017 EUR (€)	Jun. 30, 2017 CAD	Jun. 30, 2017 USD ($)
Maximum
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Foreign currency forward contract notional amount						$ 177,600,000.0
Interest expense
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of pre-tax losses in AOCI expect to be reclassified into interest expense		$ 12,400,000
Forward-starting interest rate swaps
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Foreign currency forward contract notional amount						2,500,000,000
Cross-currency rate swaps, maturity date			Mar. 31, 2021
Forward-starting interest rate swaps | Interest expense
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Net unrealized loss remaining in AOCI			$ 84,600,000
Forward-starting interest rate swaps | Interest rate swaps outstanding
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Type of interest rate paid on swap			fixed
Cross currency interest rate contract
Derivative Instruments and Hedging Activities Disclosures [Line Items]
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]
Foreign currency forward contract notional amount					CAD 6,753.5	5,000,000,000
Cross currency interest rate contract | United States dollar
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Foreign currency forward contract notional amount						5,000,000,000
Hedge Funds | Cross currency interest rate contract | Fixed income interest rate
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Foreign currency forward contract notional amount				€ 1,107,800,000.0		$ 1,200,000,000