Summary of Significant Accounting Policies (Cash and Cash Equivalents) (Details)	12 Months Ended
Dec. 31, 2018
Maximum [Member] \| Cash And Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Investment maturity period	90 days

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_CashAndCashEquivalentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration