Debt with Commercial Bank (Narrative) (Details)			3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 17, 2016 USD ($) Companies	Aug. 05, 2014	Jun. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Oct. 14, 2015 USD ($)
Line of Credit Facility [Line Items]
Document Period End Date				Jun. 30, 2017
Debt Instrument, Periodic Payment, Principal				$ (6,250,000)	$ 0
Proceeds from Lines of Credit				60,000,000
Deferred Costs, Current			$ 136,000	136,000		$ 136,000	$ 0
Deferred Costs, Noncurrent			401,000	401,000		401,000	$ 452
Secured Syndicated Credit Facility, Second Amendment [Member] | Regions Bank [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 400,000,000
Credit agreement, maximum borrowing capacity	$ 500,000,000
Number of Participating Banks | Companies	11
Newly Added Number of Participating Banks | Companies	7
Deferred Costs, Credit Card Origination Costs, Amount			2,840,000	2,840,000		2,840,000
Secured Syndicated Credit Facility, Second Amendment [Member] | Secured Term Loan [Member] | Regions Bank [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 125,000,000
Line of Credit Facility, Term	5 years
Debt Instrument, Periodic Payment, Principal				6,000,000
Loans Payable			112,500,000	112,500,000		112,500,000
Loans Payable, Current			12,500,000	12,500,000		$ 12,500,000
Line of Credit Facility, Short Term						12 months
Line of Credit Facility, Periodic Payment, Principal			3,130,000
Short-term Debt			12,500,000	12,500,000		$ 12,500,000
Long-term Debt, Gross			100,000,000	100,000,000		100,000,000
Deferred Costs, Credit Card Origination Costs, Amount			$ 537,000	$ 537,000		$ 537,000
Line of credit, interest rate at period end			3.56%	3.56%		3.56%
Deferred Costs, Current			$ 136,000	$ 136,000		$ 136,000
Deferred Costs, Noncurrent			401,000	401,000		401,000
Secured Syndicated Credit Facility, Second Amendment [Member] | Revolving Credit Facility [Member] | Regions Bank [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 275,000,000
Line of Credit Facility, Term	5 years
Deferred Costs, Credit Card Origination Costs, Amount			$ 2,260,000	$ 2,260,000		$ 2,260,000
Line of credit, interest rate at period end			3.56%	3.56%		3.56%
Secured Syndicated Credit Facility [Member] | Regions Bank [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Term		5 years
Secured Syndicated Credit Facility [Member] | Revolving Credit Facility [Member] | Regions Bank [Member]
Line of Credit Facility [Line Items]
Credit agreement, amount outstanding			$ 214,029,000	$ 214,029,000		$ 214,029,000
Secured Syndicated Credit Facility [Member] | Revolving Credit Facility [Member] | Citi Bank [Member]
Line of Credit Facility [Line Items]
Credit agreement, average amount outstanding during period				177,400,000
Credit agreement, maximum amount outstanding during period				$ 214,000,000
Secured Syndicated Credit Facility, First Amendment [Member] | Revolving Credit Facility [Member] | Regions Bank [Member]
Line of Credit Facility [Line Items]
Credit agreement, maximum borrowing capacity								$ 240,000,000