Loans and Allowance for Loan Losses - Recorded Investment in Loans, Excluding Loans Acquired (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Loans	$ 11,858,195	$ 10,779,685
Loans, Excluding Acquired Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	47,354	43,923
Loans collectively evaluated for impairment	8,075,920	5,661,686
Total Loans	8,123,274	5,705,609
Loans, Excluding Acquired Loans \| Other Consumer and Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	3,317	4,605
Loans collectively evaluated for impairment	401,633	302,451
Total Loans	404,950	307,056
Loans, Excluding Acquired Loans \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	17,308	7,610
Loans collectively evaluated for impairment	1,809,812	965,909
Total Loans	1,827,120	973,519
Loans, Excluding Acquired Loans \| Real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	26,401	31,538
Loans collectively evaluated for impairment	5,682,666	4,208,074
Total Loans	5,709,067	4,239,612
Loans, Excluding Acquired Loans \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Loans	441,718	465,516
Loans, Excluding Acquired Loans \| Consumer \| Credit cards
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans individually evaluated for impairment	328	170
Loans collectively evaluated for impairment	181,809	185,252
Total Loans	$ 182,137	$ 185,422

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

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The balance of financing receivables that were individually evaluated for impairment.

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- Definition

Amount before allowance and after 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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

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