Income Taxes (Details Textual)	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Valuation Allowance [Line Items]
Deferred Tax Assets, Other	$ 379,000	$ 0
Income Taxes (Textual) [Abstract]
U.S. federal statutory corporate tax rate	35.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	21.00%
deferred tax effect - tax cut job act benefit	$ (73,028,000)	$ 0	$ 0
Deferred Income Tax Expense (Benefit)	(46,063,000)	14,162,000	11,884,000
Provision for income taxes	$ 5,561,000	$ 80,306,000	$ 88,172,000
Effective tax rate	2.50%	35.30%	48.40%
number of foreign subsidiaries	2
Deferred Tax Liabilities, Net	$ 15,000,000
Deferred Tax Liabilities, Net, Noncurrent	124,404,000	$ 161,502,000
No unrecognized tax benefits	1,000,000.0	$ 0
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	800,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	200,000
U.S.
Income Taxes (Textual) [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Impairment Losses			$ 0
Foreign [Member]
Income Taxes (Textual) [Abstract]
Operating Loss Carryforwards	122,000,000
State [Member]
Income Taxes (Textual) [Abstract]
Operating Loss Carryforwards	$ 261,900,000
Minimum [Member]
Income Taxes (Textual) [Abstract]
Operating Loss Carryforwards, Expiration Dates	Dec. 31, 2018
Maximum [Member]
Income Taxes (Textual) [Abstract]
Operating Loss Carryforwards, Expiration Dates	Dec. 31, 2037