Fair Value Measurements - Segregated by Level of Valuation Inputs (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financial assets:
Cash and cash equivalents	$ 525,457	$ 239,973
Securities held to maturity	15,399	603,360
Portfolio loans, net	6,616,450	5,517,780
Financial liabilities:
Short-term borrowings	29,739
Junior subordinated debt owed to unconsolidated trusts	71,269	71,155
Level 1 \| Carrying Amount
Financial assets:
Cash and cash equivalents	525,457	239,973
Level 1 \| Fair Value
Financial assets:
Cash and cash equivalents	525,457	239,973
Level 2 \| Carrying Amount
Financial assets:
Securities held to maturity	15,170	608,660
Accrued interest receivable	29,408	22,314
Financial liabilities:
Time deposits	1,652,971	1,497,003
Securities sold under agreements to repurchase	202,500	185,796
Short-term borrowings	29,739
Long-term debt	85,106	50,000
Junior subordinated debt owed to unconsolidated trusts	71,269	71,155
Accrued interest payable	7,487	6,568
Level 2 \| Fair Value
Financial assets:
Securities held to maturity	15,399	603,360
Accrued interest receivable	29,408	22,314
Financial liabilities:
Time deposits	1,654,955	1,482,301
Securities sold under agreements to repurchase	202,500	185,796
Short-term borrowings	29,835
Long-term debt	85,238	49,873
Junior subordinated debt owed to unconsolidated trusts	73,292	65,182
Accrued interest payable	7,487	6,568
Level 3 \| Carrying Amount
Financial assets:
Portfolio loans, net	6,616,450	5,517,780
Mortgage servicing rights	9,276	3,315
Other servicing rights	1,039	781
Level 3 \| Fair Value
Financial assets:
Portfolio loans, net	6,630,255	5,473,063
Mortgage servicing rights	11,410	11,051
Other servicing rights	1,676	1,443
Level 3 \| Senior notes \| Carrying Amount
Financial liabilities:
Long-term debt	39,640	39,539
Level 3 \| Senior notes \| Fair Value
Financial liabilities:
Long-term debt	40,144	39,452
Level 3 \| Subordinated debt \| Carrying Amount
Financial liabilities:
Long-term debt	59,222	59,147
Level 3 \| Subordinated debt \| Fair Value
Financial liabilities:
Long-term debt	$ 60,971	$ 58,186

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The sum of cash and cash equivalents plus Federal Funds Sold. Cash and cash equivalents consist of short term, highly liquid investments that are readily convertible to known amounts of cash and are so near their maturity that they present negligible risk of changes in value due to changes in interest rates -- usually with an original maturity less than 90 days.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Amount of interest payable on debt, including, but not limited to, trade payables.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Fair value portion of securities that an entity sells and agrees to repurchase at a specified date for a specified price.

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