Supplementary Balance Sheet Information - Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Supplementary Balance Sheet Information
Accrued card brand fees	$ 63,887	$ 55,991
Accrued third-party commissions	53,705	46,977
Accrued expenses	28,431	25,178
Dividends payable	23,780	24,645
Accrued interest	21,818	22,191
Other	86,451	93,168
Total	$ 278,072	$ 268,150