Other Borrowed Funds (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Federal Home Loan Bank advances
Other borrowed funds	$ 1,195,225,000	$ 733,375,000
Federal home loan bank advances maturing November 2027
Federal Home Loan Bank advances
Other borrowed funds	100,000,000
Federal home loan Bank advances maturing December 20207
Federal Home Loan Bank advances
Other borrowed funds	150,000,000
Federal Home Loan Bank advances - short-term
Federal Home Loan Bank advances
Other borrowed funds	$ 945,225,000	$ 583,375,000
Rate on balance outstanding at year end (as a percent)	1.44%	0.66%
Average daily balance	$ 839,858,000	$ 483,379,000
Average rate (as a percent)	1.23%	0.47%
Maximum amount outstanding at any month end	$ 1,043,250,000	$ 600,875,000
Federal Home Loan Bank advances - long-term
Federal Home Loan Bank advances
Other borrowed funds	$ 250,000,000	$ 150,000,000
Rate on balance outstanding at year end (as a percent)	1.26%	0.58%
Average daily balance	$ 51,644,000	$ 150,000,000
Average rate (as a percent)	1.26%	0.58%
Maximum amount outstanding at any month end	$ 250,000,000	$ 150,000,000

Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822

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The calculated average balance outstanding for the year for all Federal Home Loan Bank advances as of the Balance Sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(3)(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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The calculated weighted average interest rate for Federal Home Loan Bank advances outstanding as of the Balance Sheet date.

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The calculated weighted average interest rate for Federal Home Loan Bank advances for the period ended as of the Balance Sheet date.

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The maximum balance outstanding at any month end during the period as of the Balance Sheet date.

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