Debt with Commercial Bank (Narrative) (Details)			3 Months Ended		12 Months Ended
	Jun. 17, 2016 USD ($) Companies	Aug. 05, 2014	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2017	Dec. 31, 2016 USD ($)	Oct. 14, 2015 USD ($)
Line of Credit Facility [Line Items]
Document Period End Date			Mar. 31, 2017
Debt Instrument, Periodic Payment, Principal			$ (3,125,000)	$ 0
Proceeds from Lines of Credit			40,000,000
Deferred Costs, Current			136,000			$ 0
Deferred Costs, Noncurrent			435,000			$ 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			3,000,000
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			3,000,000
Loans Payable			115,600,000
Loans Payable, Current			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
Long-term Debt, Gross			103,100,000
Deferred Costs, Credit Card Origination Costs, Amount			$ 571,000
Line of credit, interest rate at period end			3.06%
Deferred Costs, Current			$ 136,000
Deferred Costs, Noncurrent			435,000
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			$ 2,400,000
Line of credit, interest rate at period end			3.06%
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			$ 194,029,000
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			160,200,000
Credit agreement, maximum amount outstanding during period			$ 194,000,000
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