Securities Available-for-Sale - Amortized Cost and Fair Value of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 681,758	$ 686,205
Fair Value	689,388	693,487
Obligations of the U.S. Treasury, U.S. government corporations and agencies, and obligations of states and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Amortized Cost	61,661
Due after one year through five years, Amortized Cost	180,806
Due after five years through ten years, Amortized Cost	58,782
Due after ten years, Amortized Cost	59,591
Available-for-sale Securities, Debt Maturities, Amortized Cost	360,840
Due in one year or less, Fair Value	61,805
Due after one year through five years, Fair Value	182,760
Due after five years through ten years, Fair Value	60,214
Due after ten years, Fair Value	62,647
Fair Value, Debt securities	367,426
Collateralized mortgage obligations of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	120,272	130,046
Fair Value	120,203	129,777
Residential mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	33,850	36,606
Fair Value	34,611	37,358
Commercial mortgage-backed securities of U.S. government corporations and agencies
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	162,981	127,311
Fair Value	162,413	125,604
Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	677,943	678,626
Fair Value	684,653	682,238
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,815	7,579
Fair Value	$ 4,735	$ 11,249