Investment Securities - Investments' Gross Unrealized Losses and Fair Value Aggregated by Investment Category and Length of Time in Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	$ 330,902	$ 90,954
Less than 12 Months, Gross Unrealized Losses	9,674	505
12 Months or Longer, Fair Value		2,101
12 Months or Longer, Gross Unrealized Losses		73
Total, Fair Value	330,902	93,055
Total, Gross Unrealized Losses	9,674	578
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	179,395	69,641
Less than 12 Months, Gross Unrealized Losses	3,802	519
12 Months or Longer, Fair Value		14,888
12 Months or Longer, Gross Unrealized Losses		283
Total, Fair Value	179,395	84,529
Total, Gross Unrealized Losses	3,802	802
Available-for-sale Securities and Held-to-maturity Securities [Abstract]
Less than 12 Months, Fair Value	510,297	160,595
Less than 12 Months, Gross Unrealized Losses	13,476	1,024
12 Months or Longer, Fair Value		16,989
12 Months or Longer, Gross Unrealized Losses		356
Total, Fair Value	510,297	177,584
Total, Gross Unrealized Losses	13,476	1,380
State and municipal
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	126,593	7,558
Less than 12 Months, Gross Unrealized Losses	5,564	60
12 Months or Longer, Fair Value
12 Months or Longer, Gross Unrealized Losses
Total, Fair Value	126,593	7,558
Total, Gross Unrealized Losses	5,564	60
U.S. Government-sponsored mortgage-backed securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	185,544	83,396
Less than 12 Months, Gross Unrealized Losses	3,071	445
12 Months or Longer, Fair Value		2,101
12 Months or Longer, Gross Unrealized Losses		73
Total, Fair Value	185,544	85,497
Total, Gross Unrealized Losses	3,071	518
Equity securities
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	18,765
Less than 12 Months, Gross Unrealized Losses	1,039
Total, Fair Value	18,765
Total, Gross Unrealized Losses	1,039
Government Agency and Municipal Bonds and Notes
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	19,121
Less than 12 Months, Gross Unrealized Losses	479
Total, Fair Value	19,121
Total, Gross Unrealized Losses	479
State and municipal
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	50,897
Less than 12 Months, Gross Unrealized Losses	1,796
12 Months or Longer, Fair Value		1,982
12 Months or Longer, Gross Unrealized Losses		15
Total, Fair Value	50,897	1,982
Total, Gross Unrealized Losses	1,796	15
U.S. Government-sponsored mortgage-backed securities
Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract]
Less than 12 Months, Fair Value	109,377	69,641
Less than 12 Months, Gross Unrealized Losses	1,527	519
12 Months or Longer, Fair Value		12,906
12 Months or Longer, Gross Unrealized Losses		268
Total, Fair Value	109,377	82,547
Total, Gross Unrealized Losses	$ 1,527	$ 787