Guarantor and Non-Guarantor Subsidiaries Financial Information - Consolidating Statement of Cash Flows (Parenthetical) Unaudited (Detail)	Mar. 31, 2019	Mar. 31, 2018
3.625% Senior Secured Notes due 2026
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	3.625%
4.125% Senior Secured Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	4.125%
4.875% Senior Secured Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	4.875%
5.625% Senior Secured Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	5.625%
5.50% Senior Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	5.50%	5.50%
6.75% Senior Notes
Condensed Cash Flow Statements Captions [Line Items]
Interest rate	6.75%	6.75%