Loans - Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Average recorded investment
Impaired loans with a valuation allowance	$ 68,157	$ 39,131
Impaired loans with no related valuation allowance	37,754	85,936
Total impaired loans	105,911	125,067
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	264	333
Impaired loans with no related valuation allowance	563	663
Total impaired loans	827	996
Commercial
Average recorded investment
Impaired loans with a valuation allowance	25,712	10,551
Impaired loans with no related valuation allowance	9,297	31,404
Total impaired loans	35,009	41,955
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	0	0
Impaired loans with no related valuation allowance	255	277
Total impaired loans	255	277
Commercial real estate
Average recorded investment
Impaired loans with a valuation allowance	20,035	7,592
Impaired loans with no related valuation allowance	23,473	45,737
Total impaired loans	43,508	53,329
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	0	0
Impaired loans with no related valuation allowance	306	380
Total impaired loans	306	380
Real estate construction and land development
Average recorded investment
Impaired loans with a valuation allowance	161	0
Impaired loans with no related valuation allowance	81	918
Total impaired loans	242	918
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	0	0
Impaired loans with no related valuation allowance	2	6
Total impaired loans	2	6
Residential mortgage
Average recorded investment
Impaired loans with a valuation allowance	17,398	20,988
Impaired loans with no related valuation allowance	3,808	5,149
Total impaired loans	21,206	26,137
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	264	333
Impaired loans with no related valuation allowance	0	0
Total impaired loans	264	333
Consumer installment
Average recorded investment
Impaired loans with a valuation allowance	780	0
Impaired loans with no related valuation allowance	215	340
Total impaired loans	995	340
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	0	0
Impaired loans with no related valuation allowance	0	0
Total impaired loans	0	0
Home equity
Average recorded investment
Impaired loans with a valuation allowance	4,071	0
Impaired loans with no related valuation allowance	880	2,388
Total impaired loans	4,951	2,388
Interest income recognized while on impaired status
Impaired loans with a valuation allowance	0	0
Impaired loans with no related valuation allowance	0	0
Total impaired loans	$ 0	$ 0