Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 0	$ 0	$ 96,000
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal	63,496,000	49,769,000	41,721,000
Current State and Local Tax Expense (Benefit)	860,000	0	48,000
Total current tax expense (benefit)	64,356,000	49,769,000	41,769,000
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Federal	26,339,000	12,776,000	4,963,000
State	1,826,000	1,614,000	857,000
Total deferred tax expense (benefit)	59,651,000	14,390,000	5,819,000
Income tax expense (benefit)	$ 124,006,536	64,159,167	47,588,528
Federal income tax statutory rate	35.00%
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense (benefit) at statutory rate	$ 104,295,000	66,984,000	50,084,000
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount	1,746,000	1,049,000	588,000
Tax-exempt securities	5,666,000	2,510,000	2,543,000
Federal tax credits	(434,000)	(282,000)	0
Bank owned life insurance	2,778,000	(1,242,000)	892,000
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Life Insurance, Amount	(283,000)	(159,000)	(306,000)
Deferred tax revaluation expense	31,486,000	0	0
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount	(5,365,000)	0	0
Effective Income Tax Rate Reconciliation, Tax Contingency, Amount	0	0	0
Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount	1,006,000	319,000	658,000
Income tax expense (benefit)	124,006,536	64,159,167	47,588,528
Deferred Tax Assets, Net [Abstract]
Loan loss allowance	16,240,000	22,308,000
Loans	46,567,000	15,534,000
Insurance	614,000	869,000
Accrued liability for supplemental retirement agreements	7,413,000	5,587,000
Restricted stock and stock options	8,232,000	8,643,000
Investments	0	4,275,000
Cash flow hedge	499,000	1,520,000
Equity Method Investments	635,000	858,000
Leases	1,738,000	1,627,000
Net operating loss carryforward	18,085,000	0
Other real estate owned	2,809,000	149,000
Other deferred tax assets	5,373,000	6,413,000
Total deferred tax assets	108,205,000	67,783,000
Deferred Tax Liabilities, Net [Abstract]
Depreciation and amortization	11,504,000	5,823,000
Core deposit intangible asset	14,073,000	5,621,000
Securities	616,000	0
REIT dividends	3,073,000	4,602,000
FHLB related liabilities	922,000	285,000
Debt Issuance Costs	1,077,000	1,001,000
Other deferred tax liabilities	1,171,000	679,000
Total deferred tax liabilities	32,436,000	18,011,000
Net deferred tax assets	75,769,000	49,772,000
Unrecognized tax benefits, beginning of period	1,274,000	134,000	391,000
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions	1,564,000	1,140,000
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions			(257,000)
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	0	0	0
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	0	0
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities	0	0	0
Unrecognized tax benefits, end of period	$ 2,838,000	$ 1,274,000	$ 134,000