Debt - Schedule of Debt Redemption Prices (Details) - Senior Notes - Senior Notes 9.50% due 2024	12 Months Ended
	Dec. 31, 2017
Debt Instrument [Line Items]
Debt redemption price (as a percent)	109.50%
2019
Debt Instrument [Line Items]
Debt redemption price (as a percent)	107.125%
2020
Debt Instrument [Line Items]
Debt redemption price (as a percent)	104.75%
2021
Debt Instrument [Line Items]
Debt redemption price (as a percent)	102.375%
2022 and thereafter
Debt Instrument [Line Items]
Debt redemption price (as a percent)	100.00%