Fair Value Measurements (Details 4) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	$ 72,563	$ 161,215
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	15,879	12,885
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	56,684	148,330
Non Purchased Credit Impaired Loans and Leases
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	63,463	149,749
Non Purchased Credit Impaired Loans and Leases | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	0	0
Non Purchased Credit Impaired Loans and Leases | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	6,779	1,661
Non Purchased Credit Impaired Loans and Leases | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	56,684	148,088
Other real estate and foreclosed assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	9,100	11,224
Other real estate and foreclosed assets | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	0	0
Other real estate and foreclosed assets | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	9,100	11,224
Cost-method Investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans		242
Cost-method Investments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans		0
Cost-method Investments | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans		0
Cost-method Investments | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans		242
Third party appraisals | Other real estate and foreclosed assets | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired Non‑PCI loans	$ 0	$ 0