Cash and Cash Equivalents - Additional Information (Detail) $ in Millions	9 Months Ended
Sep. 30, 2017 USD ($) Institution	Dec. 31, 2016 USD ($)
Cash And Cash Equivalents [Abstract]
Financial institutions to held securities \| Institution	2
Cash and cash equivalents original maturity dates	Three months or less
Bank balances \| $	$ 3.7	$ 2.1

An element designated to encapsulate any additional information related to cash and cash equivalents not otherwise addressed by the existing taxonomy. Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

No definition available.

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