Summary of Significant Accounting Policies (Details)	3 Months Ended												12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares	Sep. 30, 2017 $ / shares	Jun. 30, 2017 $ / shares	Mar. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($) $ / shares	Sep. 30, 2016 $ / shares	Jun. 30, 2016 $ / shares	Mar. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2015 $ / shares	Jun. 30, 2015 $ / shares	Mar. 31, 2015 $ / shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 shares	Dec. 31, 2017 USD ($)	Dec. 31, 2017 market	Dec. 31, 2017 Rate	Dec. 31, 2017 shares	Dec. 31, 2016 USD ($) shares
Schedule of Equity Method Investments [Line Items]
Deferred tax asset/liability revaluation													$ 31,485,672	$ 0	$ 0
Number of Markets in Which Entity Operates | market																		11
Goodwill [Roll Forward]
Balance at December 31, 2016				$ 551,593,796									551,593,796
Goodwill, Acquired During Period													1,256,455,000
Goodwill, Purchase Accounting Adjustments													0
Goodwill, Other Increase (Decrease)													(47,000)
Balance at December 31, 2017	$ 1,808,001,781				$ 551,593,796								1,808,001,781	551,593,796
Finite-lived Intangible Assets [Roll Forward]
Balance at December 31, 2016				15,104,000									15,104,000
Acquisitions													50,422,000
Amortization													(8,815,609)	(4,281,459)	(1,973,953)
Change in purchase price allocation of previous acquisitions													0
Other changes													0
Balance at December 31, 2017	56,710,391				15,104,000								56,710,391	15,104,000
Balance at December 31, 2016				566,697,796									566,697,796
Acquisitions													1,306,877,000
Amortization													(8,815,609)
Change in purchase price allocation of previous acquisitions													0
Other changes													(47,000)
Balance at December 31, 2017	1,864,712,172				566,697,796								1,864,712,172	566,697,796
Finite-Lived Intangible Assets, Net [Abstract]
Finite-Lived Intangible Assets, Gross																	$ 92,787,000				$ 42,365,000
Accumulated amortization																	(36,077,000)				(27,261,000)
Net book value	$ 56,710,391			$ 15,104,000	$ 15,104,000								$ 15,104,000	15,104,000			56,710,391				15,104,000
Cash Equivalents and Cash Flows [Abstract]
Cash equivalents maturity period													90 days
Cash Payments [Abstract]
Interest													$ 91,628,041	37,002,870	17,435,292
Income taxes paid													81,538,510	49,503,637	45,715,968
Noncash Transactions [Abstract]
Loans charged-off to the allowance for loan losses													(22,046,511)	(31,112,118)	(21,148,034)
Real Estate Owned, Transfer to Real Estate Owned													6,227,509	4,453,060	341,342
Loans foreclosed upon with repossessions transferred to other repossessed assets													645,737	1,842,318	8,259,368
Other real estate sales financed													907,931	0	0
Common stock issued in connection with acquisitions													$ 1,850,968,026	222,162,640	269,492,990
Loans [Abstract]
Number of loan segments													5
Net deferred loan fees													$ 7,800,000	7,600,000
Percentage of loan portfolio assigned specific risk rating	81.40%												81.40%
Premises and Equipment and Leaseholds [Abstract]
Deferred liability associated with escalating rentals																	3,500,000
Other Assets [Abstract]
Premises and equipment, net																	266,013,608				88,904,145
Amortization													$ 2,500,000	2,300,000	1,300,000
Cash surrender value of life insurance																	415,900,000				150,600,000
Noninterest income related to cash surrender value of bank owned life insurance policies													7,900,000	3,500,000	2,500,000
investments are included in CRA investments																	23,900,000				18,900,000
Investments as per community reinvestment act																	44,000,000				43,100,000
Variable Interest Entity [Line Items]
Federal Reserve Bank and Federal Home Loan Bank (FHLB) stock																	46,400,000				31,400,000
Investments in other entities at fair value																	24,400,000				8,300,000
Gain (loss) due to change in fair value of investments													$ (552,310)	(233,000)
Number of trusts investment	12												12
Value of investments with trust companies																	221,667,490				205,359,844
Other Real Estate Owned [Abstract]
Other real estate owned																	29,100,000				6,500,000
Valuation allowance related to other real estate owned																	1,224,066				400,000
Foreclosed real estate expense													$ 1,079,000	$ 396,000	(306,000)
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued									$ (96,000)						$ (96,000)		0				$ 0
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock options outstanding (in shares) | shares									1,251,601						1,251,601	698,488				274,586	550,490
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements | shares													567,611	694,909	958,320
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount | shares													0
Basic earnings per share calculation [Abstract]
Numerator - Net income (loss) available to common stockholders													$ 173,979,487	$ 127,224,695	$ 95,509,402
Denominator - Weighted average common shares outstanding (in shares) | shares													63,760,578	43,037,083	37,015,468
Basic net income per common share (in dollars per share) | $ / shares	$ 0.35	$ 0.84	$ 0.81	$ 0.83	$ 0.79	$ 0.71	$ 0.75	$ 0.70	$ 0.67	$ 0.64	$ 0.65	$ 0.62	$ 2.73	$ 2.96	$ 2.58
Diluted net income per share calculation [Abstract]
Numerator - Net income (loss) available to common stockholders													$ 173,979,487	$ 127,224,695	$ 95,509,402
Denominator - Weighted average common shares outstanding (in shares) | shares													63,760,578	43,037,083	37,015,468
Dilutive shares (in shares) | shares													567,611	694,909	958,320
Weighted average diluted common shares outstanding (in shares) | shares													64,328,189	43,731,992	37,973,788
Diluted net income per common share (in dollars per share) | $ / shares	$ 0.35	$ 0.83	$ 0.80	$ 0.82	$ 0.78	$ 0.71	$ 0.73	$ 0.68	$ 0.65	$ 0.62	$ 0.64	$ 0.62	$ 2.70	$ 2.91	$ 2.52
Mortgage Servicing Rights [Abstract]
Servicing Asset at Amortized Cost									$ 6,412,000						$ 6,412,000
Mortgage servicing rights associated with Fannie Mae portfolio								$ 830,000,000
Proceeds from sale of mortgage servicing rights								6,600,000					$ 0	$ 6,747,626	$ 0
Income Recorded from Sale of Mortgage Servicing Portfolio								$ 241,000						241,000
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Value of investments with trust companies																	3,995,000
Small Impaired Loans [Member]
Financing Receivable, Impaired [Line Items]
Principal balance of loans subject to individual determination of impairment																	500,000
Premises and Equipment [Member] | Minimum
Premises and Equipment and Leaseholds [Abstract]
Premises and equipment, useful life													3 years
Premises and Equipment [Member] | Maximum
Premises and Equipment and Leaseholds [Abstract]
Premises and equipment, useful life													30 years
Computer Software, Intangible Asset [Member]
Other Assets [Abstract]
Premises and equipment, net																	$ 9,300,000				$ 5,700,000
Computer Software, Intangible Asset [Member] | Minimum
Premises and Equipment and Leaseholds [Abstract]
Premises and equipment, useful life													3 years
Computer Software, Intangible Asset [Member] | Maximum
Premises and Equipment and Leaseholds [Abstract]
Premises and equipment, useful life													7 years
Bankers Healthcare Group, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	49.00%												49.00%						49.00%
Finite-lived Intangible Assets [Roll Forward]
Amortization													$ (3,300,000)	$ (3,400,000)
Internal Revenue Service (IRS) [Member] | Minimum
Income Tax Contingency [Line Items]
Tax year open to audit under the statute of limitation																2014
Internal Revenue Service (IRS) [Member] | Maximum
Income Tax Contingency [Line Items]
Tax year open to audit under the statute of limitation													2017
Employee Stock Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock options outstanding (in shares) | shares																				274,586
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction in tax expense due to ASU 2016-09													$ 5,400,000