Investments (Number of Securities Included in Loss Position of Current and Noncurrent Investments) (Details)	Dec. 31, 2014 Securities
Current [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	469
12 Months or More	166
Total number of securities	635
Current [Member] | Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	124
12 Months or More	51
Total number of securities	175
Current [Member] | U.S. government and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	4
12 Months or More	0
Total number of securities	4
Current [Member] | Obligations of states and other political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	21
12 Months or More	46
Total number of securities	67
Current [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	320
12 Months or More	69
Total number of securities	389
Noncurrent [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	9
12 Months or More	1
Total number of securities	10
Noncurrent [Member] | Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	0
12 Months or More	1
Total number of securities	1
Noncurrent [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months	9
12 Months or More	0
Total number of securities	9