Lease Obligations (Operating Leases) (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jan. 01, 2019	Dec. 31, 2018
Operating Leased Assets [Line Items]
Operating lease assets	$ 233,423		$ 233,423			$ 0
Operating leases, additions	20,000		86,000
Operating leases, variable lease costs	3,100		7,500
Operating leases, short-term leases, expense	144,000		352,400
Lease Term in Excess of One Year [Member]
Operating Leased Assets [Line Items]
Operating leases, expense	$ 29,500		$ 84,800
Operating leases, rent and related expense		$ 33,100		$ 85,400
Lease Term in Excess of One Year [Member] | Minimum [Member]
Operating Leased Assets [Line Items]
Operating leases, term of contract (in years)	1 year	1 year	1 year	1 year
Lease Term of One Year or Less [Member]
Operating Leased Assets [Line Items]
Operating leases, rent and related expense		$ 142,700		$ 339,400
Lease Term of One Year or Less [Member] | Maximum [Member]
Operating Leased Assets [Line Items]
Operating leases, term of contract (in years)	1 year	1 year	1 year	1 year
ASU 2016-02 [Member]
Operating Leased Assets [Line Items]
Operating lease assets					$ 230,000