Investments (Number of Securities Included in Loss Position of Current and Noncurrent Investments) (Details)	Dec. 31, 2015 Securities
Current [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	850
12 Months or More	85
Total number of securities	935
Current [Member] | Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	266
12 Months or More	39
Total number of securities	305
Current [Member] | U.S. government and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	8
12 Months or More	0
Total number of securities	8
Current [Member] | Obligations of states and other political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	71
12 Months or More	14
Total number of securities	85
Current [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	505
12 Months or More	32
Total number of securities	537
Noncurrent [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	21
12 Months or More	9
Total number of securities	30
Noncurrent [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	21
12 Months or More	9
Total number of securities	30