Commercial Bank Financing Facility (Details) - USD ($)			12 Months Ended
	Aug. 05, 2014	May. 20, 2014	Dec. 31, 2015	Dec. 31, 2014	Oct. 14, 2015	Feb. 03, 2015	Aug. 31, 2014	May. 19, 2014
Secured Syndicated Credit Facility | Regions Bank
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 150,000,000
Deferred Costs, Credit Card Origination Costs, Amount			$ 1,600,000
Secured Syndicated Credit Facility | Revolving Credit Facility | Regions Bank
Line of Credit Facility [Line Items]
Line of Credit Facility, Expansion	50,000,000
Line of Credit, Accordion	$ 50,000,000				$ 50,000,000
Debt Instrument, Term	5 years
Current Borrowing Capacity	$ 150,000,000
Credit agreement, maximum borrowing capacity	$ 200,000,000
Line of credit, interest rate at period end			1.94%
Secured Syndicated Credit Facility | Revolving Credit Facility | Citi Bank
Line of Credit Facility [Line Items]
Debt instrument, face amount								$ 100,000,000
Credit agreement, amount outstanding			$ 206,460,000	$ 120,500,000				$ 7,840,000
Repayments of Lines of Credit		$ 15,000,000
Line of credit, interest rate at period end			2.25%
Credit agreement, average amount outstanding during period			$ 156,200,000
Credit agreement, maximum amount outstanding during period			$ 206,460,000
Weighted average interest rate			2.00%	1.94%
Secured Syndicated Credit Facility, First Amendment [Member] | Revolving Credit Facility | Regions Bank
Line of Credit Facility [Line Items]
Line of Credit Facility, Expansion						$ 90,000,000
Debt instrument, face amount						190,000,000
Credit agreement, maximum borrowing capacity					240,000,000	$ 240,000,000
Secured Syndicated Credit Facility, First Amendment [Member] | Revolving Credit Facility | TD Bank [Member]
Line of Credit Facility [Line Items]
Credit agreement, maximum borrowing capacity					$ 25,000,000
Secured Term Loan | Secured Syndicated Credit Facility | Citi Bank
Line of Credit Facility [Line Items]
Repayments of term loan				$ 7,600,000
Other Long-term Debt							$ 0
Minimum [Member] | Secured Syndicated Credit Facility | Regions Bank
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	1.75%
Maximum [Member] | Secured Syndicated Credit Facility | Regions Bank
Line of Credit Facility [Line Items]
Basis spread on variable interest rate	2.25%