Securities (Details) - Remaining Contractual Maturity of Securities - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Available-for-sale Securities, Amortized Cost Basis [Abstract]
One year or less	$ 84,587
After one year to five years	430,910
After five years to ten years	6,333
After ten years	48,219
Securities that do not have a single contractual maturity date	1,193,764
Amortized Cost	1,763,813	$ 1,324,146
Available-for-sale Securities, Fair Value [Abstract]
One year or less	83,558
After one year to five years	425,669
After five years to ten years	6,256
After ten years	47,632
Securities that do not have a single contractual maturity date	1,210,644
Total securities available-for-sale	1,773,759	1,306,636
Held-to-maturity Securities, Amortized Cost [Abstract]
One year or less	3,220
After one year to five years	7,840
After five years to ten years	2,111
After ten years	7,501
Securities that do not have a single contractual maturity date	0
Amortized Cost	20,672	23,152
Held-to-maturity Securities, Fair Value [Abstract]
One year or less	2,865
After one year to five years	6,976
After five years to ten years	1,878
After ten years	6,675
Securities that do not have a single contractual maturity date	0
Total	$ 18,394	$ 20,054