Debt - Debt (Detail)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013
Convertible Debt
Line of Credit Facility [Line Items]
Average interest rate	3.75%	3.75%
Variable and fixed interest rates ranging, minimum		3.75%	3.75%
Senior Secured Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Average interest rate	8.50%	8.50%
Minimum | Other Indebtedness
Line of Credit Facility [Line Items]
Variable and fixed interest rates ranging, minimum	5.00%
Maximum | Other Indebtedness
Line of Credit Facility [Line Items]
Variable and fixed interest rates ranging, minimum	5.50%