Covered Assets and Indemnification Asset - Aging (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Covered Assets and Indemnification Asset
Total loans	$ 6,148,813	$ 5,843,499
Covered
Covered Assets and Indemnification Asset
Total Past Due Loans	7,803	6,777
Current Loans	92,024	115,596
Total loans	190,410	256,127
Accruing Loans Past Due 90 Days or More		173
Covered | Financing Receivables, 30 to 59 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans	4,024	3,622
Covered | Financing Receivables, 60 to 89 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans	2,296	1,580
Covered | Financing Receivables, Equal to Greater than 90 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans	1,483	1,575
Covered | PCI loans
Covered Assets and Indemnification Asset
Total loans	90,583	133,754
Covered | Secured
Covered Assets and Indemnification Asset
Total Past Due Loans	43	102
Current Loans	918	1,083
Total loans	1,201	2,398
Accruing Loans Past Due 90 Days or More		44
Covered | Secured | Financing Receivables, 60 to 89 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans		6
Covered | Secured | Financing Receivables, Equal to Greater than 90 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans	43	96
Covered | Secured | PCI loans
Covered Assets and Indemnification Asset
Total loans	240	1,213
Covered | Unsecured
Covered Assets and Indemnification Asset
Total loans	41	299
Covered | Unsecured | PCI loans
Covered Assets and Indemnification Asset
Total loans	41	299
Covered | Secured by Commercial Properties
Covered Assets and Indemnification Asset
Total Past Due Loans	71	325
Current Loans	12,724	19,132
Total loans	38,493	72,094
Covered | Secured by Commercial Properties | Financing Receivables, 30 to 59 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans	71	96
Covered | Secured by Commercial Properties | Financing Receivables, 60 to 89 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans		229
Covered | Secured by Commercial Properties | PCI loans
Covered Assets and Indemnification Asset
Total loans	25,698	52,637
Covered | Secured by Residential Properties
Covered Assets and Indemnification Asset
Total Past Due Loans	7,681	6,335
Current Loans	76,285	91,639
Total loans	148,284	172,375
Accruing Loans Past Due 90 Days or More		129
Covered | Secured by Residential Properties | Financing Receivables, 30 to 59 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans	3,945	3,511
Covered | Secured by Residential Properties | Financing Receivables, 60 to 89 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans	2,296	1,345
Covered | Secured by Residential Properties | Financing Receivables, Equal to Greater than 90 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans	1,440	1,479
Covered | Secured by Residential Properties | PCI loans
Covered Assets and Indemnification Asset
Total loans	64,318	74,401
Covered | Commercial construction loans and land development
Covered Assets and Indemnification Asset
Total Past Due Loans	8	15
Current Loans	2,097	3,742
Total loans	2,391	8,961
Covered | Commercial construction loans and land development | Financing Receivables, 30 to 59 Days Past Due
Covered Assets and Indemnification Asset
Total Past Due Loans	8	15
Covered | Commercial construction loans and land development | PCI loans
Covered Assets and Indemnification Asset
Total loans	$ 286	$ 5,204