Loans and Allowance for Credit Losses - Loans by class and credit quality indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Loans	$ 7,880,255	$ 7,545,748
Pass
Loans		7,356,769
Watch
Loans		109,313
Special Mention
Loans		11,460
Substandard
Loans		68,206
Commercial
Loans	1,524,613	1,545,906
Commercial | Pass
Loans	1,405,399	1,470,636
Commercial | Watch
Loans	32,881	38,522
Commercial | Special Mention
Loans	20,742	11,460
Commercial | Substandard
Loans	65,591	25,288
Income producing - commercial real estate
Loans	3,724,839	3,702,747
Income producing - commercial real estate | Pass
Loans	3,349,617	3,667,585
Income producing - commercial real estate | Watch
Loans	197,859	16,069
Income producing - commercial real estate | Special Mention
Loans	16,084
Income producing - commercial real estate | Substandard
Loans	161,279	19,093
Owner occupied - Commercial real estate
Loans	997,645	985,409
Owner occupied - Commercial real estate | Pass
Loans	808,834	925,800
Owner occupied - Commercial real estate | Watch
Loans	54,612	53,146
Owner occupied - Commercial real estate | Substandard
Loans	134,199	6,463
Real estate mortgage residential
Loans	82,385	104,221
Real estate mortgage residential | Pass
Loans	76,438	98,228
Real estate mortgage residential | Watch
Loans	4,766	628
Real estate mortgage residential | Substandard
Loans	1,181	5,365
Construction - commercial and residential
Loans	879,144	1,125,244
Construction - commercial and residential | C & I Owner Occupied
Loans	140,357	89,490
Construction - commercial and residential | Pass
Loans	850,388	1,113,734
Construction - commercial and residential | Watch
Loans	25,629
Construction - commercial and residential | Substandard
Loans	3,127	11,510
Home equity
Loans	72,648	80,061
Home equity | Pass
Loans	70,894	78,626
Home equity | Watch
Loans	1,450	948
Home equity | Substandard
Loans	304	487
Other consumer
Loans	2,509	2,160
Other consumer | Pass
Loans	2,499	$ 2,160
Other consumer | Substandard
Loans	$ 10