Summary of Significant Accounting Policies - Narrative (Details)			3 Months Ended		6 Months Ended
	Jun. 16, 2017 shares	Jan. 27, 2017 USD ($) shares	Jun. 30, 2017 USD ($) market	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) market shares	Jun. 30, 2016 USD ($)
Schedule of Equity Method Investments [Line Items]
Number of markets entity operates | market			11		11
Reduction in tax expense | $			$ (19,987,812)	$ (15,758,582)	$ (33,778,834)	$ (29,594,439)
Accounting Standards Update 2016-09 - Stock Compensation Improvements to Employee Share-Based Payment Activity
Schedule of Equity Method Investments [Line Items]
Reduction in tax expense | $			$ 789,000		$ 4,600,000
Common Stock | BNC Bancorp
Schedule of Equity Method Investments [Line Items]
Common stock issued in conjunction with acquisition (in shares) | shares	27,687,100				27,687,100
Underwritten public offering
Schedule of Equity Method Investments [Line Items]
Shares issued (in shares) | shares		3,220,000
Net proceeds of offering | $		$ 192,200,000
Over-allotment option
Schedule of Equity Method Investments [Line Items]
Shares issued (in shares) | shares		420,000
Bankers Healthcare Group, LLC
Schedule of Equity Method Investments [Line Items]
Ownership interest (as percent)			49.00%		49.00%