Loans (Summary of Information Related to Impaired Loans) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule representing information related to impaired loans
Average recorded investment related to impaired loans	$ 145,923	$ 138,197	$ 135,942	$ 133,845
Interest income recognized related to loans with impaired status	3,286	1,213	5,615	3,545
Commercial [Member]
Schedule representing information related to impaired loans
Average recorded investment related to impaired loans	43,812	42,847	42,478	39,387
Interest income recognized related to loans with impaired status	1,073	310	1,750	862
Commercial real estate [Member]
Schedule representing information related to impaired loans
Average recorded investment related to impaired loans	58,658	59,150	56,779	59,927
Interest income recognized related to loans with impaired status	1,219	470	2,068	1,453
Real estate construction and land development [Member]
Schedule representing information related to impaired loans
Average recorded investment related to impaired loans	2,400	2,210	2,243	2,338
Interest income recognized related to loans with impaired status	64	26	115	89
Residential mortgage [Member]
Schedule representing information related to impaired loans
Average recorded investment related to impaired loans	35,986	30,467	30,499	29,084
Interest income recognized related to loans with impaired status	818	387	1,540	1,098
Consumer installment [Member]
Schedule representing information related to impaired loans
Average recorded investment related to impaired loans	601	497	439	474
Interest income recognized related to loans with impaired status	17	0	19	1
Home equity [Member]
Schedule representing information related to impaired loans
Average recorded investment related to impaired loans	4,466	3,026	3,504	2,635
Interest income recognized related to loans with impaired status	$ 95	$ 20	$ 123	$ 42