Fair Value Measurements (Supply Commitment) (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Supply Commitment [Line Items]
Outstanding financial letters of credit	$ 7,287
Less than one year [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	5,917
More than one year to five years [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	363
Over five years [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	1,007
Secured [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	6,924
Secured [Member] | Less than one year [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	5,554
Secured [Member] | More than one year to five years [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	363
Secured [Member] | Over five years [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	1,007
Secured by Collateral [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	4,519
Secured by Collateral [Member] | Less than one year [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	3,149
Secured by Collateral [Member] | More than one year to five years [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	363
Secured by Collateral [Member] | Over five years [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	1,007
Secured by Bank Lines of Credit [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	2,405
Secured by Bank Lines of Credit [Member] | Less than one year [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	2,405
Unsecured [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	363
Unsecured [Member] | Less than one year [Member]
Supply Commitment [Line Items]
Outstanding financial letters of credit	$ 363