Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Interest and Debt Expense [Abstract]
Interest incurred on debt	$ 6,217	$ 4,819	$ 12,086	$ 9,716
Accretion of fair value adjustment on Senior Notes	1,609	1,571	3,208	3,134
Amortization of debt issuance costs	76	46	154	46
Total interest expense	$ 7,902	$ 6,436	$ 15,448	$ 12,896
Effective interest rate, revolving credit facility			5.98%		5.52%
Stated interest rate	6.375%		6.375%