Derivative Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flow Hedging
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Maximum length of future cash flow hedges	9 years 7 months 6 days
Recognized gain and losses on the ineffective portion	$ 0	$ 0	$ 0
Accumulated net loss on derivative contracts included in accumulated other comprehensive loss expected to be recognized in the Consolidated Statements of Comprehensive Income in the following 12 months, net of tax	3,700,000
Gain (losses) reclassified out of AOCI into net income based on the probability that the original forecasted transaction would not occur	0	$ (300,000)	$ 0
Interest-Rate Contracts
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Notional amount of outstanding contracts	2,878,400,000
Notional maturities for interest-rate contracts 2018	978,500,000
Notional maturities for interest-rate contracts 2019	911,200,000
Notional maturities for interest-rate contracts 2020	436,900,000
Notional maturities for interest-rate contracts 2021	392,300,000
Notional maturities for interest-rate contracts 2022	126,800,000
Notional maturities for interest-rate contracts thereafter	32,700,000
Foreign-exchange contracts
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Derivative notional amount outstanding	$ 480,400,000
Foreign-exchange contracts maturity period	within one year