Fair Value of Financial Instruments - Carrying Amount and Estimated Fair Value of Financial Instruments (Details) - USD ($)		3 Months Ended		12 Months Ended
		Mar. 31, 2019		Dec. 31, 2018
Financial assets:
Securities held-to-maturity		$ 199,010,000		$ 193,131,000
Quoted market prices in an active market (Level 1)
Financial assets:
Securities held-to-maturity		0		0
Loans, net		0		0
Consumer loans held-for-sale		0		0
Commercial loans held-for-sale		0		0
Financial liabilities:
Deposits and securities sold under agreements to repurchase		0		0
Federal Home Loan Bank advances		0		0
Subordinated debt and other borrowings		0		0
Off-balance sheet instruments:
Commitments to extend credit	[1]	0		0
Standby letters of credit	[2]	0		0
Models with significant observable market parameters (Level 2)
Financial assets:
Securities held-to-maturity		199,010,000		193,131,000
Loans, net		0		0
Consumer loans held-for-sale		54,613,000		34,929,000
Commercial loans held-for-sale		14,713,000		16,296,000
Financial liabilities:
Deposits and securities sold under agreements to repurchase		0		0
Federal Home Loan Bank advances		0		0
Subordinated debt and other borrowings		0		0
Off-balance sheet instruments:
Commitments to extend credit	[1]	0		0
Standby letters of credit	[2]	0		0
Models with significant unobservable market parameters (Level 3)
Financial assets:
Securities held-to-maturity		0		0
Loans, net		17,916,901,000		17,288,795,000
Consumer loans held-for-sale		0		0
Commercial loans held-for-sale		0		0
Financial liabilities:
Deposits and securities sold under agreements to repurchase		17,977,271,000		18,337,848,000
Federal Home Loan Bank advances		2,109,609,000		1,432,003,000
Subordinated debt and other borrowings		465,615,000		464,616,000
Off-balance sheet instruments:
Commitments to extend credit	[1]	1,729,000		1,733,000
Standby letters of credit	[2]	1,135,000		1,131,000
Carrying/ Notional Amount
Financial assets:
Securities held-to-maturity		194,043,000		194,282,000
Loans, net		18,087,712,000		17,623,974,000
Consumer loans held-for-sale		53,658,000		34,196,000
Commercial loans held-for-sale		14,456,000		15,954,000
Financial liabilities:
Deposits and securities sold under agreements to repurchase		18,581,159,000		18,953,848,000
Federal Home Loan Bank advances		2,121,075,000		1,443,589,000
Subordinated debt and other borrowings		484,703,000		485,130,000
Off-balance sheet instruments:
Commitments to extend credit	[1]	7,397,175,000		6,921,689,000
Standby letters of credit	[2]	191,279,000		177,475,000
Estimated Fair Value
Financial assets:
Securities held-to-maturity	[3]	199,010,000		193,131,000
Loans, net	[3]	17,916,901,000		17,288,795,000
Consumer loans held-for-sale	[3]	54,613,000		34,929,000
Commercial loans held-for-sale	[3]	14,713,000		16,296,000
Financial liabilities:
Deposits and securities sold under agreements to repurchase	[3]	17,977,271,000		18,337,848,000
Federal Home Loan Bank advances	[3]	2,109,609,000		1,432,003,000
Subordinated debt and other borrowings	[3]	465,615,000		464,616,000
Off-balance sheet instruments:
Commitments to extend credit	[1],[3]	1,729,000		1,733,000
Standby letters of credit	[2],[3]	1,135,000		1,131,000
Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Gain (Loss) On Impaired loans, net		(1,113,000)	[4]	(1,214,000)
Gain (Loss) on Other real estate owned		$ 50,000		$ (84,000)

[1] At the end of each quarter, Pinnacle Financial evaluates the inherent risks of the outstanding off-balance sheet commitments. In making this evaluation, Pinnacle Financial evaluates the credit worthiness of the borrower, the collateral supporting the commitments and any other factors similar to those used to evaluate the inherent risks of our loan portfolio. Additionally, Pinnacle Financial evaluates the probability that the outstanding commitment will eventually become a funded loan. As a result, at both March 31, 2019 and December 31, 2018, Pinnacle Financial included in other liabilities $1.7 million representing the inherent risks associated with these off-balance sheet commitments.

[2] At both March 31, 2019 and December 31, 2018, the aggregate fair value of Pinnacle Financial's standby letters of credit was $1.1 million. These amounts represent the unamortized fee associated with these standby letters of credit and are included in the consolidated balance sheets of Pinnacle Financial and are believed to approximate fair value. These fair values will decrease over time as the existing standby letters of credit approach their expiration dates.

[3] Estimated fair values are consistent with an exit-price concept. The assumptions used to estimate the fair values are intended to approximate those that a market-participant would realize in a hypothetical orderly transaction.

[4] Amount is net of valuation allowance of $5.5 million and $4.0 million at March 31, 2019 and December 31, 2018, respectively, as required by ASC 310-10, "Receivables."