Fair Value Measurements - Carrying Values and Estimated Fair Values of Financial Instruments (Parenthetical) (Details)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Credit Facility, Secured Due January 2022
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instruments maturity month and year	2022-01
Term Loan, Secured, Due April 2024
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instruments maturity month and year	2024-04
Second Lien Notes, Secured, Due July 2024
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instruments maturity month and year	2024-07
6.875% Notes, Unsecured, Due April 2022
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instruments maturity month and year	2022-04
Stated interest rate	6.875%	6.875%
7.125% Notes, Unsecured, Due April 2025
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instruments maturity month and year	2025-04
Stated interest rate	7.125%	7.125%