Fair Value Measurements (Narrative) (Details)	Dec. 31, 2017 USD ($)
Non-recurring fair value measurements [Abstract]
Fair Value Measurements, Nonrecurring	$ 0

Aggregation of the liabilities reported on the balance sheet measured at fair value on a nonrecurring basis by the entity.

No definition available.

Name:	us-gaap_LiabilitiesFairValueDisclosureNonrecurring
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant