Description of Business and Significant Accounting Policies (Details) $ in Billions	Mar. 31, 2018 USD ($)
Description of Business and Significant Accounting Policies
Assets under management	$ 80.2

The carrying amount of assets an investment adviser manages on behalf of investors.

No definition available.

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