Fair Value Measurements (Details 1) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Securities available‑for‑sale	$ 3,341,335	$ 3,559,437
Equity warrants		4,914
Level 1
Securities available‑for‑sale		71,942
Level 2
Securities available‑for‑sale		3,388,054
Level 3
Securities available‑for‑sale		99,441
Equity warrants	5,108
Government agency and government-sponsored enterprise pass through securities
Securities available‑for‑sale	528,941	667,840
Government agency and government-sponsored enterprise collateralized mortgage obligations
Securities available‑for‑sale	157,231	194,755
Municipal securities
Securities available‑for‑sale	1,522,494	1,547,331
Government agency and government-sponsored enterprise commercial mortgage-backed securities
Securities available‑for‑sale	531,273	391,441
Corporate debt securities
Securities available‑for‑sale	49,011	48,424
Collateralized loan obligations
Securities available‑for‑sale	156,647	132,189
SBA securities
Securities available‑for‑sale	187,300	211,157
US Treasury securities
Securities available‑for‑sale	0	69,380
US Government-sponsored Enterprises Debt Securities
Securities available‑for‑sale	0	36,913
Asset-backed and other securities
Securities available‑for‑sale	69,813	115,211
Fair Value, Measurements, Recurring
Securities available‑for‑sale	3,341,335
Derivative assets	1,261	11,919
Total recurring assets	3,347,704	3,576,270
Derivative liabilities	1,829	1,397
Fair Value, Measurements, Recurring | Level 1
Securities available‑for‑sale	2,177	71,942
Derivative assets	0	0
Equity warrants	0	0
Total recurring assets	2,177	71,942
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 2
Securities available‑for‑sale	3,261,313	3,388,054
Derivative assets	1,261	11,919
Equity warrants	0	0
Total recurring assets	3,262,574	3,399,973
Derivative liabilities	1,829	1,397
Fair Value, Measurements, Recurring | Level 3
Securities available‑for‑sale	77,845	99,441
Derivative assets	0	0
Equity warrants	5,108	4,914
Total recurring assets	82,953	104,355
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise pass through securities | Level 1
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise pass through securities | Level 2
Securities available‑for‑sale	528,941	667,840
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise pass through securities | Level 3
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise collateralized mortgage obligations | Level 1
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise collateralized mortgage obligations | Level 2
Securities available‑for‑sale	157,231	194,755
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise collateralized mortgage obligations | Level 3
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Private Label Collateralized Mortgage Obligations | Level 1
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Private Label Collateralized Mortgage Obligations | Level 2
Securities available‑for‑sale	75,804	63,555
Fair Value, Measurements, Recurring | Private Label Collateralized Mortgage Obligations | Level 3
Securities available‑for‑sale	62,821	81,241
Fair Value, Measurements, Recurring | Municipal securities | Level 1
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Municipal securities | Level 2
Securities available‑for‑sale	1,522,494	1,547,331
Fair Value, Measurements, Recurring | Municipal securities | Level 3
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise commercial mortgage-backed securities | Level 1
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise commercial mortgage-backed securities | Level 2
Securities available‑for‑sale	531,273	391,441
Fair Value, Measurements, Recurring | Government agency and government-sponsored enterprise commercial mortgage-backed securities | Level 3
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Corporate debt securities | Level 1
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Corporate debt securities | Level 2
Securities available‑for‑sale	49,011	48,424
Fair Value, Measurements, Recurring | Corporate debt securities | Level 3
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 1
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 2
Securities available‑for‑sale	156,647	132,189
Fair Value, Measurements, Recurring | Collateralized loan obligations | Level 3
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | SBA securities | Level 1
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | SBA securities | Level 2
Securities available‑for‑sale	187,300	211,157
Fair Value, Measurements, Recurring | SBA securities | Level 3
Securities available‑for‑sale	0	0
Fair Value, Measurements, Recurring | US Treasury securities | Level 1
Securities available‑for‑sale		69,380
Fair Value, Measurements, Recurring | US Treasury securities | Level 2
Securities available‑for‑sale		0
Fair Value, Measurements, Recurring | US Treasury securities | Level 3
Securities available‑for‑sale		0
Fair Value, Measurements, Recurring | US Government-sponsored Enterprises Debt Securities | Level 1
Securities available‑for‑sale		0
Fair Value, Measurements, Recurring | US Government-sponsored Enterprises Debt Securities | Level 2
Securities available‑for‑sale		36,913
Fair Value, Measurements, Recurring | US Government-sponsored Enterprises Debt Securities | Level 3
Securities available‑for‑sale		0
Fair Value, Measurements, Recurring | Asset-backed and other securities | Level 1
Securities available‑for‑sale	2,177	2,562
Fair Value, Measurements, Recurring | Asset-backed and other securities | Level 2
Securities available‑for‑sale	52,612	94,449
Fair Value, Measurements, Recurring | Asset-backed and other securities | Level 3
Securities available‑for‑sale	$ 15,024	$ 18,200