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Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt discount.

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Weighted average interest rate of debt outstanding.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Borrowings and Other Short-term Liabilities (Schedule of Short- and Long-term Borrowings) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Aug. 31, 2016
Short Term Borrowings and Long Term Debt [Line Items]
Long-term borrowings, Amount	$ 426,002	$ 372,882
Long-term borrowings, Weighted Average Rate	2.11%	1.47%
Total borrowings	$ 2,461,002	$ 2,372,882
Total short-term and long-term borrowings, Weighted Average Rate	2.41%	1.40%
FHLB advances: 2.46% - 2.59% fixed-rate notes \| Minimum
Short Term Borrowings and Long Term Debt [Line Items]
Stated interest rate	2.46%
FHLB advances: 2.46% - 2.59% fixed-rate notes \| Maximum
Short Term Borrowings and Long Term Debt [Line Items]
Stated interest rate	2.59%
Federal Home Loan Bank Advances \| FHLB advances: 1.00% - 2.72% fixed-rate notes due 2019 to 2025(2)
Short Term Borrowings and Long Term Debt [Line Items]
Long-term borrowings, Amount	$ 410,102	$ 337,204
Long-term borrowings, Weighted Average Rate	2.00%	1.26%
Advances payable from Federal Home Loan Banks	$ 410,000	$ 337,000
Purchase accounting premiums	$ 100	200
Federal Home Loan Bank Advances \| FHLB advances: 1.00% - 2.72% fixed-rate notes due 2019 to 2025(2) \| Minimum
Short Term Borrowings and Long Term Debt [Line Items]
Stated interest rate	1.00%
Federal Home Loan Bank Advances \| FHLB advances: 1.00% - 2.72% fixed-rate notes due 2019 to 2025(2) \| Maximum
Short Term Borrowings and Long Term Debt [Line Items]
Stated interest rate	2.72%
Line of Credit
Short Term Borrowings and Long Term Debt [Line Items]
Long-term borrowings, Amount	$ 0	$ 19,963	$ 125,000
Long-term borrowings, Weighted Average Rate	0.00%	3.10%
Line of Credit \| LIBOR
Short Term Borrowings and Long Term Debt [Line Items]
Basis spread on variable rate	1.75%
Subordinated Debt Obligations \| Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035
Short Term Borrowings and Long Term Debt [Line Items]
Long-term borrowings, Amount	$ 11,572	$ 11,425
Long-term borrowings, Weighted Average Rate	4.85%	3.69%
Purchase accounting discounts	$ 3,400	$ 3,600
Advances payable	$ 15,000	15,000
Subordinated Debt Obligations \| Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035 \| Minimum \| LIBOR
Short Term Borrowings and Long Term Debt [Line Items]
Basis spread on variable rate	1.45%
Subordinated Debt Obligations \| Subordinated debt obligations: floating-rate based on three-month LIBOR plus 1.45% - 2.85% due 2034 to 2035 \| Maximum \| LIBOR
Short Term Borrowings and Long Term Debt [Line Items]
Basis spread on variable rate	2.85%
Subordinated Debt Obligations \| Subordinated debt obligations: floating-rate based on three-month LIBOR plus 3.25% due in 2032
Short Term Borrowings and Long Term Debt [Line Items]
Long-term borrowings, Amount	$ 4,328	$ 4,290
Long-term borrowings, Weighted Average Rate	5.65%	4.59%
Purchase accounting discounts	$ 700	$ 700
Advances payable	$ 5,000	5,000
Subordinated Debt Obligations \| Subordinated debt obligations: floating-rate based on three-month LIBOR plus 3.25% due in 2032 \| LIBOR
Short Term Borrowings and Long Term Debt [Line Items]
Basis spread on variable rate	3.25%
Collateralized Customer Deposits
Short Term Borrowings and Long Term Debt [Line Items]
Short-term borrowings, Amount	$ 382,687	$ 415,236
Weighted average interest rate	0.75%	0.44%
Federal Home Loan Bank Advances \| FHLB advances: 2.46% - 2.59% fixed-rate notes
Short Term Borrowings and Long Term Debt [Line Items]
Short-term borrowings, Amount	$ 2,035,000	$ 2,000,000
Weighted average interest rate	2.47%	1.39%