Summary of Significant Accounting Policies Leases (Details)	12 Months Ended
Dec. 31, 2017
Minimum
Operating Leased Assets
Lessee Leasing Arrangements, Operating Leases, Term of Contract	15 years
Maximum
Operating Leased Assets
Lessee Leasing Arrangements, Operating Leases, Term of Contract	20 years

Term of the lessee's leasing arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_LesseeLeasingArrangementsOperatingLeasesTermOfContract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration