Investments Schedule of Available-for-sale and Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Available-for-sale securities at fair value:
Amortized Cost	$ 961,351	$ 966,900
Unrealized Gains	32,182	15,002
Unrealized Losses	(367)	(3,618)
Fair Value	993,166	978,284
Held-to-maturity securities at amortized cost:
Amortized Cost	45,395	48,212
Unrealized Gains	731	53
Unrealized Losses	(30)	(316)
Fair Value	46,096	47,949
Equity securities at fair value:
Amortized Cost	23,080	18,810
Fair Value	23,080	18,810
U.S. government and agencies
Available-for-sale securities at fair value:
Amortized Cost	19,957	19,955
Unrealized Gains	1,130	42
Unrealized Losses	0	(57)
Fair Value	21,087	19,940
Government-sponsored entities
Available-for-sale securities at fair value:
Amortized Cost	154,844	154,963
Unrealized Gains	5,598	1,292
Unrealized Losses	0	0
Fair Value	160,442	156,255
Municipal bonds
Available-for-sale securities at fair value:
Amortized Cost	319,844	312,977
Unrealized Gains	12,784	12,551
Unrealized Losses	(128)	(73)
Fair Value	332,500	325,455
Mortgage-backed securities
Available-for-sale securities at fair value:
Amortized Cost	466,706	479,005
Unrealized Gains	12,670	1,117
Unrealized Losses	(239)	(3,488)
Fair Value	479,137	476,634
Held-to-maturity securities at amortized cost:
Amortized Cost	45,395	48,212
Unrealized Gains	731	53
Unrealized Losses	(30)	(316)
Fair Value	46,096	47,949
Money market mutual funds
Equity securities at fair value:
Amortized Cost	23,080	18,810
Fair Value	$ 23,080	$ 18,810

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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