Fair Value Measurements (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	800,000
Securities available‑for‑sale	3,223,830,000	$ 3,559,437,000
Warrants Not Settleable in Cash, Fair Value Disclosure		4,914,000
Threshold for loans that are considered individually significant for allowance analysis purposes		250,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available‑for‑sale		99,441,000
Warrants Not Settleable in Cash, Fair Value Disclosure		4,914,000
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available‑for‑sale	3,223,830,000	3,559,437,000
Warrants Not Settleable in Cash, Fair Value Disclosure		4,914,000
Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available‑for‑sale	65,275,000	99,441,000
Warrants Not Settleable in Cash, Fair Value Disclosure	5,497,000	4,914,000
Private Label Collateralized Mortgage Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available‑for‑sale	125,469,000	144,796,000
Private Label Collateralized Mortgage Obligations [Member] | Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available‑for‑sale	56,902,000	81,241,000
Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available‑for‑sale	62,237,000	115,211,000
Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available‑for‑sale	$ 8,373,000
Square 1 Financial, Inc. [Member] | Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants Not Settleable in Cash, Fair Value Disclosure		4,914,000
Square 1 Financial, Inc. [Member] | Private Label Collateralized Mortgage Obligations [Member] | Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available‑for‑sale		51,500,000
Square 1 Financial, Inc. [Member] | Asset-backed Securities [Member] | Fair Value, Measurements, Recurring [Member] | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available‑for‑sale		$ 18,200,000