Debt (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) installment	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,500,000,000.0
Line of credit facility, additional borrowing capacity	$ 500,000,000
Debt instrument, interest, additional interest above eurodollar rate	1.00%
Contract notional amount	$ 893,610,000	$ 245,650,000
Line of credit facility, remaining borrowing capacity	656,000,000
Current portion of long-term debt	35,000,000	20,000,000
Long-term debt	$ 790,000,000	385,000,000
Debt instrument, interest rate at period end	2.76%
Letters of credit outstanding	$ 8,200,000
Federal Funds rate
Debt Instrument [Line Items]
Debt instrument, interest, additional interest above federal fund rate	0.50%
Euro Dollar rate | Federal Funds rate
Debt Instrument [Line Items]
Minimum applicable margin rate	0.125%
Maximum applicable margin rate	0.50%
Term loan
Debt Instrument [Line Items]
Debt instrument, maturity duration	5 years
Line of credit facility, maximum borrowing capacity	$ 400,000,000
Line of credit facility, frequency of payments in quarterly installments | installment	16
Interest rate at period end	1.80%
Debt instrument, interest base rate	0.42%
Debt instrument, interest, additional interest above base rate	1.38%
Revolver
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,100,000,000
Revolver | Letter of credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	40,000,000
Connecticut Economic Development Program
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5,000,000
Debt instrument, fixed interest rate	3.00%
Debt instrument, maturity period	10 years
Debt instrument, period principal payments are deferred	5 years
Line of credit facility, decrease, forgiveness	$ 2,500,000
Debt instrument, forgiveness period under the terms of the loan	5 years
Interest Rate Contract
Debt Instrument [Line Items]
Contract notional amount	$ 700,000,000
Interest rate swap
Debt Instrument [Line Items]
Contract notional amount	$ 700,000,000.0
Derivative, term of contract	30 days
Interest rate derivative hedge, negative fair value	$ 5,100,000	$ 2,900,000
Euro Dollar rate
Debt Instrument [Line Items]
Minimum applicable margin rate	1.125%
Maximum applicable margin rate	1.50%
Minimum | Interest rate swap
Debt Instrument [Line Items]
Derivative, fixed interest rate	1.53%
Maximum | Interest rate swap
Debt Instrument [Line Items]
Derivative, fixed interest rate	1.60%