Condensed Financial Statements of Parent Company - Statements of Cash Flows (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Cash flows from operating activities:                      
Net income $ 6,542 $ 6,248 $ 5,577 $ 5,243 $ 4,886 $ 5,266 $ 4,664 $ 4,798 $ 23,610 $ 19,614 $ 14,905
Adjustments to reconcile net income to net cash provided by operating activities:                      
Net amortization of securities discounts and premiums                 3,080 3,174 2,980
Net cash provided by operating activities                 25,887 22,737 19,660
Cash flows from investing activities:                      
Purchase of available-for-sale securities                 (153,853) (167,397) (123,504)
Proceeds from maturities/sales of available-for-sale securities                 147,413 125,736 120,772
Net cash used in investing activities                 (87,818) (194,442) (121,276)
Cash flows from financing activities:                      
Issuance of common shares                   34,897  
Proceeds related to exercise of stock options                 777 847 769
Cash dividends paid                 (5,141) (5,052) (1,177)
Net cash provided by financing activities                 87,520 166,352 54,912
Net change in cash and cash equivalents                 25,589 (5,353) (46,704)
Cash and cash equivalents, beginning of year       42,349       47,702 42,349 47,702 94,406
Cash and cash equivalents, end of year 67,938       42,349       67,938 42,349 47,702
People’s Utah Bancorp, Inc.                      
Cash flows from operating activities:                      
Net income                 23,610 19,614 14,905
Adjustments to reconcile net income to net cash provided by operating activities:                      
Equity in undistributed net income of the Banks                 (20,300) (17,023) (11,461)
Net amortization of securities discounts and premiums                 89 55  
Change in other assets and liabilities                 1,002 886 (671)
Net cash provided by operating activities                 4,401 3,532 2,773
Cash flows from investing activities:                      
Purchase of available-for-sale securities                 (20,995) (50,227)  
Proceeds from maturities/sales of available-for-sale securities                 21,267 15,149  
Return of escrow funds                     287
Net cash used in investing activities                 272 (35,078) 287
Cash flows from financing activities:                      
Issuance of common shares                   34,897  
Proceeds related to exercise of stock options                 777 847 769
Cash dividends paid                 (5,141) (5,052) (1,177)
Net cash provided by financing activities                 (4,364) 30,692 (408)
Net change in cash and cash equivalents                 309 (854) 2,652
Cash and cash equivalents, beginning of year       $ 2,637       $ 3,491 2,637 3,491 839
Cash and cash equivalents, end of year $ 2,946       $ 2,637       $ 2,946 $ 2,637 $ 3,491