Securities - HTM in an Unrealized Loss Position (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($) item
Number of Securities
Unrealized loss for less than twelve months | item	87	101
Unrealized loss for twelve months or longer | item	2	2
Total | item	89	103
Fair Value
Unrealized loss for less than twelve months	$ 253,495	$ 282,825
Unrealized loss for twelve months or longer	1,856	1,863
Total	255,351	284,688
Unrealized Losses
Unrealized loss for less than twelve months	6,440	7,043
Unrealized loss for twelve months or longer	11	13
Total	$ 6,451	$ 7,056
Bonds
Number of Securities
Unrealized loss for less than twelve months | item	4	4
Total | item	4	4
Fair Value
Unrealized loss for less than twelve months	$ 33,321	$ 33,225
Total	33,321	33,225
Unrealized Losses
Unrealized loss for less than twelve months	1,192	1,287
Total	$ 1,192	$ 1,287
Residential mortgage-backed Securities
Number of Securities
Unrealized loss for less than twelve months | item	1	2
Total | item	1	2
Fair Value
Unrealized loss for less than twelve months	$ 6,131	$ 13,178
Total	6,131	13,178
Unrealized Losses
Unrealized loss for less than twelve months	11	6
Total	$ 11	$ 6
Commercial mortgage-backed securities
Number of Securities
Unrealized loss for less than twelve months | item	4	5
Unrealized loss for twelve months or longer | item	1	1
Total | item	5	6
Fair Value
Unrealized loss for less than twelve months	$ 19,801	$ 18,891
Unrealized loss for twelve months or longer	1,395	1,401
Total	21,196	20,292
Unrealized Losses
Unrealized loss for less than twelve months	549	588
Unrealized loss for twelve months or longer	5	5
Total	$ 554	$ 593
Collateralized mortgage obligations
Number of Securities
Unrealized loss for less than twelve months | item	18	19
Total | item	18	19
Fair Value
Unrealized loss for less than twelve months	$ 169,154	$ 187,669
Total	169,154	187,669
Unrealized Losses
Unrealized loss for less than twelve months	3,077	3,372
Total	$ 3,077	$ 3,372
States and political subdivisions
Number of Securities
Unrealized loss for less than twelve months | item	60	71
Unrealized loss for twelve months or longer | item	1	1
Total | item	61	72
Fair Value
Unrealized loss for less than twelve months	$ 25,088	$ 29,862
Unrealized loss for twelve months or longer	461	462
Total	25,549	30,324
Unrealized Losses
Unrealized loss for less than twelve months	1,611	1,790
Unrealized loss for twelve months or longer	6	8
Total	$ 1,617	$ 1,798