Investment Securities (Details 3) $ in Millions	Sep. 30, 2017 USD ($)
Available-for-sale Securities, Debt Maturities [Abstract]
Debt securities with contractual maturities of one year or less	$ 350.6
Debt securities with contractual maturities exceeding one year	$ 2.6

Fair value of available-for-sale debt securities maturing in the next rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant