Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Interest and Debt Expense [Abstract]
Interest incurred on debt	$ 12,919	$ 5,870
Senior Note redemption premium	4,782	0
Accretion of fair value adjustment on Senior Notes	19,414	1,599
Accretion of original issue discount on 2018 Term Loan	88	0
Amortization of debt issuance costs	662	77
Total interest expense	$ 37,865	$ 7,546
Effective interest rate, revolving credit facility	4.57%		5.08%
Stated interest rate				6.375%
Accelerated Accretion	$ 18,700