Investment Securities Held-to-maturity Securities with Unrealized Loss (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014 securities	Dec. 31, 2013 securities
Schedule of Held-to-maturity Securities
Fair value of securities in unrealized loss position less than 12 months	$ 0	$ 38,209
Unrealized loss less than 12 months	0	3,123
Number of securities at an unrealized loss position less than 12 months	0	9
Fair value of securities in unrealized loss more than 12 months	24,921	1,181
Unrealized loss more than 12 months	672	133
Number of securities at an unrealized loss position more than 12 months	7	1
Total fair value	24,921	39,390
Unrealized loss	672	3,256
States and political subdivisions
Schedule of Held-to-maturity Securities
Fair value of securities in unrealized loss position less than 12 months	0	321
Unrealized loss less than 12 months	0	12
Number of securities at an unrealized loss position less than 12 months	0	1
Fair value of securities in unrealized loss more than 12 months	323	0
Unrealized loss more than 12 months	7	0
Number of securities at an unrealized loss position more than 12 months	1	0
Total fair value	323	321
Unrealized loss	7	12
Residential mortgage-backed securities
Schedule of Held-to-maturity Securities
Fair value of securities in unrealized loss position less than 12 months	0	31,341
Unrealized loss less than 12 months	0	2,908
Number of securities at an unrealized loss position less than 12 months	0	7
Fair value of securities in unrealized loss more than 12 months	18,242	1,181
Unrealized loss more than 12 months	394	133
Number of securities at an unrealized loss position more than 12 months	5	1
Total fair value	18,242	32,522
Unrealized loss	394	3,041
Commercial mortgage-backed securities
Schedule of Held-to-maturity Securities
Fair value of securities in unrealized loss position less than 12 months	0	6,547
Unrealized loss less than 12 months	0	203
Number of securities at an unrealized loss position less than 12 months	0	1
Fair value of securities in unrealized loss more than 12 months	6,356	0
Unrealized loss more than 12 months	271	0
Number of securities at an unrealized loss position more than 12 months	1	0
Total fair value	6,356	6,547
Unrealized loss	$ 271	$ 203