Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Securities available‑for‑sale	$ 3,559,437	$ 1,567,177
Derivative Asset	11,919	5,234
Warrants Not Settleable in Cash, Fair Value Disclosure	4,914
Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	3,559,437	1,567,177
Derivative Asset, Fair Value of Collateral	11,919	5,234
Assets, Fair Value Disclosure, Recurring	3,576,270	1,572,411
Derivative Liability, Fair Value of Collateral	1,397	118
Level 1
Securities available‑for‑sale		519
Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	71,942	519
Derivative Asset, Fair Value of Collateral	0	0
Warrants Not Settleable in Cash, Fair Value Disclosure	0
Assets, Fair Value Disclosure, Recurring	71,942	519
Derivative Liability, Fair Value of Collateral	0	0
Level 2
Securities available‑for‑sale		1,532,711
Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	3,388,054	1,532,711
Derivative Asset, Fair Value of Collateral	11,919	5,234
Warrants Not Settleable in Cash, Fair Value Disclosure	0
Assets, Fair Value Disclosure, Recurring	3,399,973	1,537,945
Derivative Liability, Fair Value of Collateral	1,397	118
Level 3
Securities available‑for‑sale		33,947
Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	99,441	33,947
Derivative Asset, Fair Value of Collateral	0	0
Warrants Not Settleable in Cash, Fair Value Disclosure	4,914
Assets, Fair Value Disclosure, Recurring	104,355	33,947
Derivative Liability, Fair Value of Collateral	0	0
Government agency and government-sponsored enterprise pass through securities
Securities available‑for‑sale	767,797	535,672
Government agency and government-sponsored enterprise pass through securities | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale		535,672
Government agency and government-sponsored enterprise pass through securities | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Government agency and government-sponsored enterprise pass through securities | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	767,797	535,672
Government agency and government-sponsored enterprise pass through securities | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Securities available‑for‑sale	486,239	277,946
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member] | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale		277,946
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	486,239	277,946
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Covered Private Label Collateralized Mortgage Obligation [Member]
Securities available‑for‑sale	29,782	33,947
Covered Private Label Collateralized Mortgage Obligation [Member] | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale		33,947
Covered Private Label Collateralized Mortgage Obligation [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Covered Private Label Collateralized Mortgage Obligation [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Covered Private Label Collateralized Mortgage Obligation [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	29,782	33,947
Other Private Label Collateralized Mortgage Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale		10,914
Other Private Label Collateralized Mortgage Obligations [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Other Private Label Collateralized Mortgage Obligations [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	63,555	10,914
Other Private Label Collateralized Mortgage Obligations [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	51,459	0
Municipal securities
Securities available‑for‑sale	1,547,331	536,116
Municipal securities | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale		536,116
Municipal securities | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Municipal securities | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	1,547,331	536,116
Municipal securities | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
US Treasury Securities [Member]
Securities available‑for‑sale	69,380	0
US Treasury Securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	69,380
US Treasury Securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0
US Treasury Securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0
Corporate Debt Securities [Member]
Securities available‑for‑sale	48,424	110,109
Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale		110,109
Corporate Debt Securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Corporate Debt Securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	48,424	110,109
Corporate Debt Securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
US Government-sponsored Enterprises Debt Securities [Member]
Securities available‑for‑sale	36,913	36,757
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale		36,757
US Government-sponsored Enterprises Debt Securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
US Government-sponsored Enterprises Debt Securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	36,913	36,757
US Government-sponsored Enterprises Debt Securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0	0
Other securities [Member]
Securities available‑for‑sale	115,211	25,716
Other securities [Member] | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale		25,716
Other securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	2,562	519
Other securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	94,449	25,197
Other securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	18,200	0
Collateralized Loan Obligations [Member]
Securities available‑for‑sale	132,189	0
Collateralized Loan Obligations [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0
Collateralized Loan Obligations [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	132,189
Collateralized Loan Obligations [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0
Asset-backed Securities [Member]
Securities available‑for‑sale	211,157	$ 0
Asset-backed Securities [Member] | Level 1 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	0
Asset-backed Securities [Member] | Level 2 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	211,157
Asset-backed Securities [Member] | Level 3 | Fair Value, Measurements, Recurring [Member]
Securities available‑for‑sale	$ 0