Investments in debt and equity securities available-for-sale - Debt Securities According to Contractual Terms (Details) $ in Thousands	Jun. 30, 2017 USD ($)
Amortized costs
In one year or less	$ 27,282
After one year through five years	278,518
After five years through ten years	230,715
After ten years	72,200
Amortized costs, total	608,715
Fair values
In one year or less	27,481
After one year through five years	284,020
After five years through ten years	232,923
After ten years	74,966
Fair values, total	$ 619,390