Investment Securities (Details 3) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Due in one year or less	$ 9,304
Due after one year through five years	104,445
Due after five years through ten years	310,318
Due after ten years	1,344,119
Total securities available-for-sale	1,768,186	$ 1,522,871
Fair Value Disclosures [Abstract]
Due in one year or less	9,373
Due after one year through five years	106,653
Due after five years through ten years	321,663
Due after ten years	1,371,675
Total securities available-for-sale	$ 1,809,364	$ 1,567,177