Related-Party Transactions - Additional Information (Detail) - USD ($)									3 Months Ended		9 Months Ended
	Oct. 06, 2015	Sep. 16, 2015	Jul. 01, 2015	Jun. 10, 2015	Apr. 01, 2015	Mar. 03, 2015	Jan. 22, 2015	Jan. 05, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Apr. 07, 2015	Dec. 31, 2014	Dec. 01, 2009
Related Party Transaction [Line Items]
Cash dividends declared per share		$ 0.21		$ 0.21		$ 0.21		$ 0.21	$ 0.21	$ 0.21	$ 0.84	$ 0.62
Dividends paid to stockholders											$ 54,370,000	$ 53,639,000
Cash dividends record date		Sep. 29, 2015		Jun. 22, 2015		Mar. 13, 2015		Jan. 13, 2015
Cash dividends paid date		Oct. 06, 2015		Jul. 01, 2015		Apr. 01, 2015		Jan. 22, 2015
Term B-2 Loans [Member]
Related Party Transaction [Line Items]
Debt instrument, balance															$ 1,405,000,000
Term B-3 Loans [Member]
Related Party Transaction [Line Items]
Debt instrument, balance													$ 280,000,000
Senior Notes [Member]
Related Party Transaction [Line Items]
Debt instrument, balance															$ 400,000,000
Blackstone and Affiliates [Member]
Related Party Transaction [Line Items]
Dividends paid to stockholders			$ 4,095,000		$ 4,095,000		$ 4,095,000
Blackstone and Affiliates [Member] | Term B-2 Loans [Member]
Related Party Transaction [Line Items]
Debt instrument, balance									$ 86,000,000		86,000,000			$ 87,000,000
Blackstone and Affiliates [Member] | Term B-3 Loans [Member]
Related Party Transaction [Line Items]
Debt instrument, balance									$ 18,000,000		$ 18,000,000
Blackstone and Affiliates [Member] | Senior Notes [Member]
Related Party Transaction [Line Items]
Debt instrument, balance														$ 65,000,000
Blackstone and Affiliates [Member] | Subsequent Event [Member]
Related Party Transaction [Line Items]
Dividends paid to stockholders	$ 4,095,000