Variable Interest Entities - Letters of Credit (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash collateral and other assets	$ 9,063	$ 9,135	$ 11,840
Expected LOC losses	3,297	4,708	3,041
Accounts payable	1,113	1,026	1,355
Maximum exposure for LOC losses	28,132	29,502	35,592
Exposure secured by titles to customers' automobiles	$ 8,200	$ 7,800	$ 9,900