Securities - Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	$ 455,716	$ 203,870
Gross Unrealized Losses, Less than 12 Months	(3,078)	(1,585)
Fair Value, Less than 12 Months	452,638	202,285
Amortized Cost, More than 12 Months	8,452	6,995
Gross Unrealized Losses, More than 12 Months	(110)	(96)
Fair Value, More than 12 Months	8,342	6,899
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	19,811	20,692
Gross Unrealized Losses, Less than 12 Months	(382)	(425)
Fair Value, Less than 12 Months	19,429	20,267
Amortized Cost, More than 12 Months	8,138	8,504
Gross Unrealized Losses, More than 12 Months	(329)	(378)
Fair Value, More than 12 Months	$ 7,809	$ 8,126
Investment Securities Continuous Unrealized Loss Position Qualitative Disclosure Abstract
AFS and HTM, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security	10	9
Securities in Unrealized Loss Position, Continuous Unrealized Loss as percent of Amortized Cost	0.79	1.04
US Treasury and Government [Member]
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	$ 217,111	$ 100,517
Gross Unrealized Losses, Less than 12 Months	(589)	(403)
Fair Value, Less than 12 Months	216,522	100,114
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	199,338	60,233
Gross Unrealized Losses, Less than 12 Months	(1,776)	(405)
Fair Value, Less than 12 Months	197,562	59,828
Amortized Cost, More than 12 Months	5,692	4,121
Gross Unrealized Losses, More than 12 Months	(47)	(25)
Fair Value, More than 12 Months	5,645	4,096
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	8,496	8,551
Gross Unrealized Losses, Less than 12 Months	(215)	(234)
Fair Value, Less than 12 Months	8,281	8,317
Amortized Cost, More than 12 Months	853	860
Gross Unrealized Losses, More than 12 Months	(31)	(33)
Fair Value, More than 12 Months	822	827
Collateralized Mortgage Backed Securities [Member]
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	28,027	29,916
Gross Unrealized Losses, Less than 12 Months	(414)	(492)
Fair Value, Less than 12 Months	27,613	29,424
Amortized Cost, More than 12 Months	2,760	2,874
Gross Unrealized Losses, More than 12 Months	(63)	(71)
Fair Value, More than 12 Months	2,697	2,803
Held-to-maturity, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	11,315	12,141
Gross Unrealized Losses, Less than 12 Months	(167)	(191)
Fair Value, Less than 12 Months	11,148	11,950
Amortized Cost, More than 12 Months	7,285	7,644
Gross Unrealized Losses, More than 12 Months	(298)	(345)
Fair Value, More than 12 Months	6,987	7,299
Corporate debt securities
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months		1,785
Gross Unrealized Losses, Less than 12 Months		(14)
Fair Value, Less than 12 Months		1,771
Obligations of municipal subdivisions
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months		236
Gross Unrealized Losses, Less than 12 Months		(1)
Fair Value, Less than 12 Months		235
CRA qualified investment fund
Available-for-sale, Continuous Unrealized Loss Position [Abstract]
Amortized Cost, Less than 12 Months	11,240	11,183
Gross Unrealized Losses, Less than 12 Months	(299)	(270)
Fair Value, Less than 12 Months	$ 10,941	$ 10,913