Schedule of Fair Value of Notes (Parenthetical) (Detail)	9 Months Ended	12 Months Ended
	Oct. 07, 2017	Dec. 31, 2016
2026 Notes
Fair Value Disclosures [Line Items]
Senior notes due year	2026	2026
2022 Notes
Fair Value Disclosures [Line Items]
Senior notes due year	2022	2022