Investments (Details 3) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investment Securities, Available-for-Sale, Amortized Cost
Due in one year or less	$ 4,386
Due after one year through five years	85,057
Due after five years through ten years	249,748
Due after ten years	1,165,707
Total	1,504,898	1,500,516
Investment Securities, Available-for-Sale, Estimated Fair Value
Due in one year or less	4,422
Due after one year through five years	85,209
Due after five years through ten years	252,685
Due after ten years	1,197,365
Available-for-sale, at fair value	$ 1,539,681	$ 1,494,745