Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ (2,448)	$ (18,451)
Effective income tax rate, percent	(29.47%)	(85.34%)
Federal Statutory income tax rate, percent	21.00%	35.00%
Total provision for income tax expense (benefit)	$ 17,600		$ 17,600