Debt - Credit Facility - Additional Information (Detail)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($) Entity ExtensionOptions	Dec. 31, 2014 USD ($)	Jun. 05, 2015 USD ($)
Debt Instrument [Line Items]
Number of wholly owned subsidiaries | Entity		4
Deferred financing costs	$ 1,928,000	$ 1,928,000
$400 Million Term Loan B [Member]
Debt Instrument [Line Items]
Total credit facility	400,000,000	$ 400,000,000	$ 400,000,000
Maturity Date		Jan. 15, 2021	Jan. 15, 2021
Spread rate added to LIBOR		2.75%	2.75%
$400 Million 5% Senior Notes [Member]
Debt Instrument [Line Items]
Senior notes, principal amount	$ 400,000,000	$ 400,000,000
Interest rate of Senior Notes	5.00%	5.00%
Senior Secured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maturity Date		Jun. 05, 2019
Number of extension options | ExtensionOptions		2
Spread rate added to LIBOR		1.60%
Senior Secured Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Fee to be paid by the company on the average unused portion		0.20%
Senior Secured Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Fee to be paid by the company on the average unused portion		0.30%
Senior Secured Revolving Credit Facility [Member] | $1 Billion Credit Facility [Member]
Debt Instrument [Line Items]
Total credit facility				$ 700,000,000
Senior Secured Term Loan Facility [Member] | $1 Billion Credit Facility [Member]
Debt Instrument [Line Items]
Total credit facility				$ 300,000,000