Securities Available-for-Sale - Fair Value and Age of Gross Unrealized Losses by Investment Category (Details)	Dec. 31, 2016 USD ($) security	Dec. 31, 2015 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	31	23
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 267,500,000	$ 213,997,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (3,472,000)	$ (1,302,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 24,014,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ (414,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	31	26
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 267,500,000	$ 238,011,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (3,472,000)	$ (1,716,000)
U.S. Treasury securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	1	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 9,811,000	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (127,000)	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	1	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 9,811,000	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (127,000)	$ 0
Obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	7	10
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 62,483,000	$ 88,584,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (383,000)	$ (379,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 14,542,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ (188,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	7	12
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 62,483,000	$ 103,126,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (383,000)	$ (567,000)
Collateralized mortgage obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	10	6
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 83,031,000	$ 61,211,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (734,000)	$ (316,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	10	6
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 83,031,000	$ 61,211,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (734,000)	$ (316,000)
Residential mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	2	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 10,022,000	$ 7,993,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (232,000)	$ (151,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	2	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 10,022,000	$ 7,993,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (232,000)	$ (151,000)
Commercial mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	10	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 96,576,000	$ 50,839,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (1,950,000)	$ (450,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 9,472,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ (226,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	10	6
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 96,576,000	$ 60,311,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (1,950,000)	$ (676,000)
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	1	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 5,577,000	$ 5,370,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (46,000)	$ (6,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	1	1
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 5,577,000	$ 5,370,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (46,000)	$ (6,000)
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	31	23
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 267,500,000	$ 213,997,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ (3,472,000)	$ (1,302,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	3
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 24,014,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ (414,000)
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	31	26
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 267,500,000	$ 238,011,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ (3,472,000)	$ (1,716,000)
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions | security	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Unrealized Losses	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions | security	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Unrealized Losses	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Number of Positions | security	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value, Total	$ 0	$ 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses, Total	$ 0	$ 0