Loans and Allowance for Loan Losses - Recorded Investment in Loans, Excluding Loans Acquired (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	$ 13,002,952	$ 11,723,171
Loans, Excluding Acquired Loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans individually evaluated for impairment	70,007	39,770
Loans collectively evaluated for impairment	9,573,358	8,390,618
Total Loans	9,643,365	8,430,388
Loans, Excluding Acquired Loans \| Other Consumer and Other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans individually evaluated for impairment	1,634	2,159
Loans collectively evaluated for impairment	546,055	318,180
Total Loans	547,689	320,339
Loans, Excluding Acquired Loans \| Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans individually evaluated for impairment	34,649	13,062
Loans collectively evaluated for impairment	2,073,923	1,926,361
Total Loans	2,108,572	1,939,423
Loans, Excluding Acquired Loans \| Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans individually evaluated for impairment	33,203	24,253
Loans collectively evaluated for impairment	6,758,818	5,942,200
Total Loans	6,792,021	5,966,453
Loans, Excluding Acquired Loans \| Credit Card
Financing Receivable, Allowance for Credit Loss [Line Items]
Total Loans	403,726	405,470
Loans, Excluding Acquired Loans \| Credit Card \| Credit cards
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans individually evaluated for impairment	521	296
Loans collectively evaluated for impairment	194,562	203,877
Total Loans	$ 195,083	$ 204,173

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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=118936363&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=118952595&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=118936363&loc=d3e5074-111524

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