Stock Options and Restricted Shares - Common Stock Options (Details) - Common stock options - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2020		Dec. 31, 2019
Number
Outstanding, beginning balance (in shares)		119,274
Granted (in shares)		0
Exercised (in shares)		(9,787)
Forfeited (in shares)		0
Outstanding, ending balance (in shares)		109,487		119,274
Additional disclosures
Options exercisable (in shares)		109,487
Weighted-average exercise price of options outstanding (in dollars per share)		$ 23.44		$ 23.45
Weighted-average contractual remaining term for options outstanding		2 years 1 month 6 days		2 years 10 months 6 days
Aggregate intrinsic value		$ 1,331	[1]	$ 4,837	[2]
Weighted- average exercise price of options exercisable (in dollars per share)		$ 23.44
Weighted-average contractual remaining term for options exercisable		2 years 1 month 6 days
Aggregate intrinsic value of options exercisable	[1]	$ 1,331
Quoted closing price of common stock (in dollars per share)		$ 35.59		$ 64.00
Number of awards used in aggregate intrinsic value (in shares)		109,487		119,274

[1] The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the quoted closing price of Pinnacle Financial common stock of $35.59 per common share at September 30, 2020 for the 109,487 options that were in-the-money at September 30, 2020.

[2] The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the quoted closing price of Pinnacle Financial common stock of $64.00 per common share at December 31, 2019 for the 119,274 options that were in-the-money at December 31, 2019.