Accumulated Other Comprehensive Income (Loss), Accumulated Other Comprehensive Income (Loss) Reclassifications (Details) - Unrealized Gain (Loss) on Available-for-Sale Securities [Member] - Reclassification out of Accumulated Other Comprehensive Income [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Component of Selling, General, and Administrative Expense	$ 817
Component of Other Income	$ 0