Fair Value Fair Value (Policies)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments, Policy [Policy Text Block]	The Company measures the fair value of restricted cash, foreign deposits, and money market funds based on quoted prices in active markets for identical assets. The fair value of the municipal bond is based on either recent trades in inactive markets or quoted market prices of similar instruments and other significant inputs derived from or corroborated by observable market data. Short-term investments are carried at amortized cost and the fair value is disclosed in Note 3, Investment Securities. The fair value of these investments is determined in the same manner as for available-for-sale securities and is considered a Level 1 measurement.