Financial Instruments (Maturity Periods for Investments) (Details)	9 Months Ended
	Sep. 30, 2015
Corporate bond securities | Minimum
Schedule of Available-for-sale Securities [Line Items]
Investment maturity term	2 months
Corporate bond securities | Maximum
Schedule of Available-for-sale Securities [Line Items]
Investment maturity term	3 years
US Government Agencies Debt Securities | Minimum
Schedule of Available-for-sale Securities [Line Items]
Investment maturity term	4 months
US Government Agencies Debt Securities | Maximum
Schedule of Available-for-sale Securities [Line Items]
Investment maturity term	3 years
Mortgage backed securities | Minimum
Schedule of Available-for-sale Securities [Line Items]
Investment maturity term	5 years
Mortgage backed securities | Maximum
Schedule of Available-for-sale Securities [Line Items]
Investment maturity term	6 years
Asset-backed securities | Minimum
Schedule of Available-for-sale Securities [Line Items]
Investment maturity term	1 year
Asset-backed securities | Maximum
Schedule of Available-for-sale Securities [Line Items]
Investment maturity term	26 years