Non-Covered Loans and Allowance for Non-Covered Loan Losses - Internal Risk Grades (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Internal risk grades of non-covered loans
Total loans	$ 5,783,853	$ 5,843,499
Noncovered
Internal risk grades of non-covered loans
Total loans	5,783,853	5,843,499
Noncovered | Pass
Internal risk grades of non-covered loans
Total loans	5,637,247	5,689,490
Noncovered | Special Mention
Internal risk grades of non-covered loans
Total loans	5,154	3,771
Noncovered | Substandard
Internal risk grades of non-covered loans
Total loans	93,687	98,806
Noncovered | Secured
Internal risk grades of non-covered loans
Total loans	1,561,355	1,597,112
Noncovered | Secured | Pass
Internal risk grades of non-covered loans
Total loans	1,495,445	1,531,895
Noncovered | Secured | Special Mention
Internal risk grades of non-covered loans
Total loans	853	72
Noncovered | Secured | Substandard
Internal risk grades of non-covered loans
Total loans	57,044	56,473
Noncovered | Unsecured
Internal risk grades of non-covered loans
Total loans	94,590	99,341
Noncovered | Unsecured | Pass
Internal risk grades of non-covered loans
Total loans	93,186	97,646
Noncovered | Unsecured | Substandard
Internal risk grades of non-covered loans
Total loans	1,404	1,695
Noncovered | Secured by Commercial Properties
Internal risk grades of non-covered loans
Total loans	2,057,984	1,955,095
Noncovered | Secured by Commercial Properties | Pass
Internal risk grades of non-covered loans
Total loans	2,001,976	1,888,231
Noncovered | Secured by Commercial Properties | Special Mention
Internal risk grades of non-covered loans
Total loans	975	3,693
Noncovered | Secured by Commercial Properties | Substandard
Internal risk grades of non-covered loans
Total loans	28,465	34,661
Noncovered | Secured by Residential Properties
Internal risk grades of non-covered loans
Total loans	794,261	861,672
Noncovered | Secured by Residential Properties | Pass
Internal risk grades of non-covered loans
Total loans	775,056	846,420
Noncovered | Secured by Residential Properties | Special Mention
Internal risk grades of non-covered loans
Total loans	3,321
Noncovered | Secured by Residential Properties | Substandard
Internal risk grades of non-covered loans
Total loans	5,691	4,763
Noncovered | Residential Construction Loans
Internal risk grades of non-covered loans
Total loans	136,354	128,652
Noncovered | Residential Construction Loans | Pass
Internal risk grades of non-covered loans
Total loans	136,354	128,624
Noncovered | Residential Construction Loans | Substandard
Internal risk grades of non-covered loans
Total loans		28
Noncovered | Commercial construction loans and land development
Internal risk grades of non-covered loans
Total loans	631,444	658,198
Noncovered | Commercial construction loans and land development | Pass
Internal risk grades of non-covered loans
Total loans	627,893	653,808
Noncovered | Commercial construction loans and land development | Substandard
Internal risk grades of non-covered loans
Total loans	838	923
Noncovered | Consumer
Internal risk grades of non-covered loans
Total loans	42,656	41,352
Noncovered | Consumer | Pass
Internal risk grades of non-covered loans
Total loans	42,128	40,789
Noncovered | Consumer | Special Mention
Internal risk grades of non-covered loans
Total loans	5	6
Noncovered | Consumer | Substandard
Internal risk grades of non-covered loans
Total loans	245	263
Noncovered | Broker-dealer
Internal risk grades of non-covered loans
Total loans	465,209	502,077
Noncovered | Broker-dealer | Pass
Internal risk grades of non-covered loans
Total loans	465,209	502,077
Noncovered | PCI loans
Internal risk grades of non-covered loans
Total loans	47,765	51,432
Noncovered | PCI loans | Secured
Internal risk grades of non-covered loans
Total loans	8,013	8,672
Noncovered | PCI loans | Secured by Commercial Properties
Internal risk grades of non-covered loans
Total loans	26,568	28,510
Noncovered | PCI loans | Secured by Residential Properties
Internal risk grades of non-covered loans
Total loans	10,193	10,489
Noncovered | PCI loans | Commercial construction loans and land development
Internal risk grades of non-covered loans
Total loans	2,713	3,467
Noncovered | PCI loans | Consumer
Internal risk grades of non-covered loans
Total loans	$ 278	$ 294