Hourglass Sands (Condensed Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Acquisition [Abstract]
Current assets	$ 82,448	$ 84,978
Total assets	425,627	515,499
Total liabilities	230,097	256,625
Total liabilities , redeemable noncontrolling interests, and stockholders' equity	$ 425,627	$ 515,499