Income Taxes (Detail Textuals) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Statutory federal income tax rate	35.00%	35.00%	35.00%
Corporate income tax rate effective in 2018	21.00%
Depreciation percentage on capital expenditures	10.00%
Discrete income tax provision adjustment related to vesting of restricted stock	$ 2,800
Discrete tax benefit adjustment	19,300
Undistributed earnings of foreign subsidiaries	8,400
Deferred tax assets, valuation allowance	3,994	$ 356
Foreign tax credits	3,592	0
Capital loss carryforwards	56
Total net income tax (refunds) payments	98,000	(42,400)	$ (7,900)
Unrecognized tax benefits	2,215,000	2,215,000	$ 26,152,000
Accrued interest and penalties	193	$ 76
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards related to state income taxes	79,100
Deferred tax assets, valuation allowance	$ 347