Covered Assets and Indemnification Asset - Internal Risk Grades (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Internal risk grades of covered loans in the portfolio
Total loans	$ 6,148,813	$ 5,843,499
Covered
Internal risk grades of covered loans in the portfolio
Total loans	190,410	256,127
Covered | PCI loans
Internal risk grades of covered loans in the portfolio
Total loans	90,583	133,754
Covered | Pass
Internal risk grades of covered loans in the portfolio
Total loans	89,481	111,432
Covered | Special Mention
Internal risk grades of covered loans in the portfolio
Total loans	438	461
Covered | Substandard
Internal risk grades of covered loans in the portfolio
Total loans	9,908	10,480
Covered | Secured
Internal risk grades of covered loans in the portfolio
Total loans	1,201	2,398
Covered | Secured | PCI loans
Internal risk grades of covered loans in the portfolio
Total loans	240	1,213
Covered | Secured | Pass
Internal risk grades of covered loans in the portfolio
Total loans	464	592
Covered | Secured | Substandard
Internal risk grades of covered loans in the portfolio
Total loans	497	593
Covered | Unsecured
Internal risk grades of covered loans in the portfolio
Total loans	41	299
Covered | Unsecured | PCI loans
Internal risk grades of covered loans in the portfolio
Total loans	41	299
Covered | Secured by Commercial Properties
Internal risk grades of covered loans in the portfolio
Total loans	38,493	72,094
Covered | Secured by Commercial Properties | PCI loans
Internal risk grades of covered loans in the portfolio
Total loans	25,698	52,637
Covered | Secured by Commercial Properties | Pass
Internal risk grades of covered loans in the portfolio
Total loans	11,832	17,996
Covered | Secured by Commercial Properties | Substandard
Internal risk grades of covered loans in the portfolio
Total loans	963	1,461
Covered | Secured by Residential Properties
Internal risk grades of covered loans in the portfolio
Total loans	148,284	172,375
Covered | Secured by Residential Properties | PCI loans
Internal risk grades of covered loans in the portfolio
Total loans	64,318	74,401
Covered | Secured by Residential Properties | Pass
Internal risk grades of covered loans in the portfolio
Total loans	75,322	90,563
Covered | Secured by Residential Properties | Special Mention
Internal risk grades of covered loans in the portfolio
Total loans	438	461
Covered | Secured by Residential Properties | Substandard
Internal risk grades of covered loans in the portfolio
Total loans	8,206	6,950
Covered | Commercial construction loans and land development
Internal risk grades of covered loans in the portfolio
Total loans	2,391	8,961
Covered | Commercial construction loans and land development | PCI loans
Internal risk grades of covered loans in the portfolio
Total loans	286	5,204
Covered | Commercial construction loans and land development | Pass
Internal risk grades of covered loans in the portfolio
Total loans	1,863	2,281
Covered | Commercial construction loans and land development | Substandard
Internal risk grades of covered loans in the portfolio
Total loans	$ 242	$ 1,476