Guarantor and Non-Guarantor Subsidiaries Financial Information - Consolidating Statement of Cash Flows (Parenthetical) Unaudited (Detail)	Dec. 31, 2017	Dec. 31, 2016
4.125% Senior Secured Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	4.125%	4.125%
4.875% Senior Secured Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	4.875%	4.875%
6.00% Senior Secured Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	6.00%	6.00%
6.25% Senior Secured Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	6.25%	6.25%
5.625% Senior Secured Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	5.625%	5.625%