Investments, Contract Maturity of Available-for-Sale Securities (Details)	Mar. 31, 2017 Company
Contract Maturity of Available-for-Sale Securities [Abstract]
One year or less	64.00%
After one year but within two years	24.00%
After two years but within three and a half years	12.00%
Total	100.00%
Percentage of available-for-sale securities with a maturity of less than two years	88.00%
Ownership Interests in Private and Public Companies [Abstract]
Number of privately-held companies in which there is an equity ownership interest of less than 20%	3
Number of publicly-held companies in which there is an equity ownership interest of less than 20%	1