Stock Options and Restricted Shares - Common Stock Options (Details) - Common stock options and stock appreciation rights - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended		12 Months Ended
		Sep. 30, 2018		Dec. 31, 2017
Number
Outstanding, beginning balance (in shares)		274,586
Granted (in shares)		0
Exercised (in shares)		(90,497)
Forfeited (in shares)		0
Outstanding, ending balance (in shares)		184,089		274,586
Weighted-Average Exercise Price
Outstanding, beginning balance (in dollars per share)		$ 21.40
Outstanding, ending balance (in dollars per share)		$ 22.67		$ 21.40
Additional disclosures
Options exercisable (in shares)		184,089
Weighted- average exercise price of options exercisable (in dollars per share)		$ 22.67
Weighted-average contractual remaining term for options outstanding		3 years 6 months 15 days		3 years 22 days
Weighted-average contractual remaining term for options exercisable		3 years 6 months 15 days
Aggregate intrinsic value		$ 6,900	[1]	$ 12,329	[2]
Aggregate intrinsic value of options exercisable	[1]	$ 6,900
Quoted closing price of common stock (in dollars per share)		$ 60.15		$ 66.3
Number of awards used in aggregate intrinsic value (in shares)		184,089		274,586

[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 $60.15 per common share at September 30, 2018 for the 184,089 options that were in-the-money at September 30, 2018.

[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 $66.30 per common share at December 31, 2017 for the 274,586 options that were in-the-money at December 31, 2017.