Debt - Summary of Debt and Capital Lease Obligations (Parenthetical) (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
$200 Million Term Loan A [Member]
Debt Instrument [Line Items]
Unamortized deferred financing costs	$ 1,474,000	$ 1,557,000
Maturity date for credit facility	May 23, 2022
Spread rate added to LIBOR	1.50%
Total credit facility	$ 200,000,000
$500 Million Term Loan B [Member]
Debt Instrument [Line Items]
Unamortized deferred financing costs	$ 7,330,000	7,595,000
Maturity date for credit facility	May 11, 2024
Spread rate added to LIBOR	2.25%
Total credit facility	$ 500,000,000
$350 Million 5% Senior Notes [Member]
Debt Instrument [Line Items]
Total Senior Notes	$ 350,000,000
Interest rate of Senior Notes	5.00%
Unamortized deferred financing costs	$ 3,101,000	3,340,000
Maturity date for credit facility	Apr. 15, 2021
$400 Million 5% Senior Notes [Member]
Debt Instrument [Line Items]
Total Senior Notes	$ 400,000,000
Interest rate of Senior Notes	5.00%
Unamortized deferred financing costs	$ 4,721,000	4,929,000
Maturity date for credit facility	Apr. 15, 2023
$700 Million Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Unamortized deferred financing costs	$ 8,456,000	$ 9,076,000
Maturity date for credit facility	May 23, 2021
Spread rate added to LIBOR	1.55%
Total credit facility	$ 700,000,000