Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense	$ 1,944	$ 11,234	$ 10,210	$ 17,487
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	8,300
Unrecognized income tax benefits including interest and penalties	4,900		4,900
Portion of unrecognized income tax benefits, expected to be recognized upon settlement of tax examinations and the expiration of various statutes of limitations within next twelve months	$ 1,100		$ 1,100
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense					$ 48,700