Summary of Significant Accounting Policies (Details)		3 Months Ended												12 Months Ended
		Dec. 31, 2016 USD ($) $ / shares	Sep. 30, 2016 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Mar. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Sep. 30, 2014 USD ($) $ / shares	Jun. 30, 2014 USD ($) $ / shares	Mar. 31, 2014 USD ($) $ / shares	Dec. 31, 2016 USD ($) Segment Quarter $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) Trust shares	Mar. 01, 2016	Dec. 31, 2015 USD ($)	Feb. 01, 2015
Goodwill [Roll Forward]
Balance at December 31, 2015					$ 432,232,255									$ 432,232,255
Acquisitions														122,672,000
Amortization														0
Change in purchase price allocation of previous acquisitions														(3,125,000)
Other changes	[1]													(185,000)
Balance at December 31, 2016		$ 551,593,796				$ 432,232,255								551,593,796	$ 432,232,255
Core deposit and other intangible assets [Roll Forward]
Balance at December 31, 2015					10,540,000									10,540,000
Acquisitions														8,845,000
Amortization														(4,281,459)	(1,973,953)	$ (947,678)
Change in purchase price allocation of previous acquisitions														0
Other changes	[1]													0
Balance at December 31, 2016		15,104,000				10,540,000								15,104,000	10,540,000
Total [Abstract]
Balance at December 31, 2015					442,772,000									442,772,000
Acquisitions														131,517,000
Amortization														(4,281,000)
Change in purchase price allocation of previous acquisitions														(3,125,000)
Other changes														(185,000)
Balance at December 31, 2016		566,698,000				442,772,000								566,698,000	442,772,000
Finite-Lived Intangible Assets, Net [Abstract]
Gross carrying amount																	$ 42,365,000		$ 33,520,000
Accumulated amortization																	(27,261,000)		(22,980,000)
Net book value		15,104,000			10,540,000	10,540,000								$ 10,540,000	10,540,000		$ 15,104,000		10,540,000
Cash Equivalents and Cash Flows [Abstract]
Cash equivalents maturity period														90 days
Cash Payments [Abstract]
Interest														$ 37,002,870	17,435,292	13,414,134
Income taxes paid														49,503,637	45,715,968	31,350,000
Noncash Transactions [Abstract]
Loans charged-off to the allowance for loan losses														31,112,118	21,148,034	7,702,661
Loans foreclosed upon with repossessions transferred to other real estate														4,453,060	341,342	4,649,852
Loans foreclosed upon with repossessions transferred to other repossessed assets														1,842,318	8,259,368	2,262,573
Common stock issued in connection with acquisitions														$ 222,162,640	269,492,990	0
Loans [Abstract]
Number of loan segments | Segment														5
Net deferred loan fees														$ 7,600,000	4,200,000
Percentage of loan portfolio assigned specific risk rating																	79.00%
ASC 450-20, Loss Contingencies [Abstract]
Number of prior quarters used for historical migration analysis | Quarter														24
Financing Receivable, Impaired [Line Items]
Principal balance of loans subject to individual determination of impairment																	$ 250,000
Principal balance of impaired loans										$ 16,705,000						16,705,000	27,577,000		29,359,000
Premises and Equipment and Leaseholds [Abstract]
Deferred liability associated with escalating rentals																	3,000,000
Other Assets [Abstract]
Computer software related assets, net																	88,904,145		77,923,607
Cash surrender value of life insurance																	150,614,120		121,918,638
Noninterest income related to cash surrender value of bank owned life insurance policies														$ 3,547,401	2,548,157	2,426,447
Variable Interest Entity [Line Items]
Federal Reserve Bank and Federal Home Loan Bank (FHLB) stock																	31,400,000		26,500,000
Investments in other entities at fair value																	$ 8,300,000		7,600,000
Gain (loss) due to change in fair value of investments														(233,000)	(39,000)
Number of trusts investment | Trust																	4
Value of investments with trust companies																	$ 205,359,844		88,880,014
Investments as per community reinvestment act																	43,100,000		17,100,000
investments are included in CRA investments																	18,900,000		3,200,000
Other Real Estate Owned [Abstract]
Other real estate owned																	6,500,000		6,600,000
Valuation allowance related to other real estate owned																	381,000		1,500,000
Foreclosed real estate expense														396,000	(306,000)	664,000
Realized losses on foreclosed real estate														$ 141,000	$ (434,000)	(552,000)
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued										140,000						$ 140,000	0		(96,000)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock options, stock appreciation rights and warrants included in earning per share calculation (in shares) | shares														694,909	958,320	403,555
Basic earnings per share calculation [Abstract]
Numerator - Net income (loss) available to common stockholders		$ 36,097,000	$ 32,377,000	$ 30,787,000	$ 27,964,000	$ 26,854,000	$ 24,149,000	$ 22,665,000	$ 21,843,000	$ 18,737,000	$ 18,197,000	$ 17,170,000	$ 16,367,000	$ 127,224,695	$ 95,509,402	$ 70,471,167
Denominator - Weighted average common shares outstanding (in shares) | shares														43,037,083	37,015,468	34,723,335
Basic net income per common share (in dollars per share) | $ / shares		$ 0.79	$ 0.71	$ 0.75	$ 0.70	$ 0.67	$ 0.64	$ 0.65	$ 0.62	$ 0.54	$ 0.52	$ 0.49	$ 0.47	$ 2.96	$ 2.58	$ 2.03
Diluted net income per share calculation [Abstract]
Numerator - Net income (loss) available to common stockholders		$ 36,097,000	$ 32,377,000	$ 30,787,000	$ 27,964,000	$ 26,854,000	$ 24,149,000	$ 22,665,000	$ 21,843,000	$ 18,737,000	$ 18,197,000	$ 17,170,000	$ 16,367,000	$ 127,224,695	$ 95,509,402	$ 70,471,167
Denominator - Weighted average common shares outstanding (in shares) | shares														43,037,083	37,015,468	34,723,335
Dilutive shares (in shares) | shares														694,909	958,320	403,555
Weighted average diluted common shares outstanding (in shares) | shares														43,731,992	37,973,788	35,126,890
Diluted net income per common share (in dollars per share) | $ / shares		$ 0.78	$ 0.71	$ 0.73	$ 0.68	$ 0.65	$ 0.62	$ 0.64	$ 0.62	$ 0.53	$ 0.52	$ 0.49	$ 0.47	$ 2.91	$ 2.52	$ 2.01
Mortgage Servicing Rights [Abstract]
Servicing asset at amortized cost																			6,412,000
Mortgage servicing rights associated with Fannie Mae portfolio					$ 830,000,000
Sale of mortgage servicing rights					$ 6,600,000									$ 6,747,626	$ 0	$ 0
Income recorded upon sale of servicing portfolio														$ 241,000
Trust [Member]
Variable Interest Entity [Line Items]
Value of investments with trust companies																	2,476,000		2,476,000
Premises and Equipment [Member] | Minimum [Member]
Premises and Equipment and Leaseholds [Abstract]
Premises and equipment, useful life														3 years
Premises and Equipment [Member] | Maximum [Member]
Premises and Equipment and Leaseholds [Abstract]
Premises and equipment, useful life														30 years
Software [Member]
Other Assets [Abstract]
Computer software related assets, net																	$ 5,724,215		$ 6,616,443
Computer software related assets, amortization														$ 2,326,927	1,346,284	$ 1,084,000
Software [Member] | Minimum [Member]
Other Assets [Abstract]
Computer software related assets, useful life														3 years
Software [Member] | Maximum [Member]
Other Assets [Abstract]
Computer software related assets, useful life														7 years
Bankers Healthcare Group, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage equity method investment					19.00%												49.00%	8.55%		30.00%
Core deposit and other intangible assets [Roll Forward]
Amortization														$ (3,400,000)	(1,300,000)
Internal Revenue Service (IRS) [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Tax year open to audit under the statute of limitation														2013
Internal Revenue Service (IRS) [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Tax year open to audit under the statute of limitation														2016
State of Tennessee [Member] | Minimum [Member]
Income Tax Contingency [Line Items]
Tax year open to audit under the statute of limitation														2013
State of Tennessee [Member] | Maximum [Member]
Income Tax Contingency [Line Items]
Tax year open to audit under the statute of limitation														2016
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock options outstanding (in shares) | shares																	550,490
ASU 2015-03 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Amount of deferred financing cost reclassified from other assets to subordinated debtAmount of deferred financing cost reclassified from other assets to subordinated debt															$ 870,000

[1] Represents options exercised related to acquisitions which occurred prior to the adoption of ASC 718-20 Compensation.