Marketable Securities - Maturities of Debt Securities Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017
Marketable Securities
Fair Value, Due within one year	$ 96,675	$ 89,477
Fair Value, Due after one year through five years		22,031
Fair Value	96,675	111,508
Net Carrying Amount, Due within one year	96,935	89,728
Net Carrying Amount, Due after one year through five years		22,149
Net Carrying Amount	$ 96,935	$ 111,877