Long-Term Debt and Financing Arrangements - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Revolving Line of Credit Facility [Member]
Line Of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 350,000,000
Revolving Line of Credit Facility [Member] | Bank Revolving Line of Credit [Member]
Line Of Credit Facility [Line Items]
Borrowings under bank revolving line of credit	0
Unused and available borrowings under bank revolving line of credit	320,300,000	$ 323,000,000.0
Standby Letters of Credit [Member]
Line Of Credit Facility [Line Items]
Outstanding letters of credit	$ 29,700,000
Standby Letters of Credit [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Letters of credit expiration year	2019
Standby Letters of Credit [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Letters of credit expiration year	2020