Investments (Details 2) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investment Securities, Available-for-Sale, Amortized Cost
Due in one year or less	$ 12,844
Due after one year through five years	303,622
Due after five years through ten years	658,572
Due after ten years	2,537,347
Total	3,512,385	$ 1,522,871
Investment Securities, Available-for-Sale, Estimated Fair Value
Due in one year or less	12,677
Due after one year through five years	304,163
Due after five years through ten years	664,076
Due after ten years	2,578,521
Available-for-sale, at fair value	$ 3,559,437	$ 1,567,177