Income Taxes (Provision for Income Taxes) (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes
Revaluation of deferred tax liability, benefit	$ (53,240)	$ 0	$ 0
State and local jurisdiction [Member]
Income Taxes
Tax credit carryforwards available for state tax purposes, net of federal impact	7,200
Net operating loss carryforwards available for state tax purposes	$ 9,500
Operating loss carryforwards available for state tax purposes, expiration year	2028
Tax credit carryforwards available for state tax purposes, expiration year	2024