Investment Securities (Details 3) $ in Millions	Sep. 30, 2015 USD ($)
Investment Securities
Debt securities with contractual maturities of one year or less	$ 754.2
Debt securities with contractual maturities exceeding one year	$ 21.8

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