Income Taxes (Schedule of Income before Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
United States	$ 64,631	$ 81,226	$ 81,049
Foreign	5,950	12,185	7,104
Income before income tax expense	$ 70,581	$ 93,411	$ 88,153