Fair Value Measurements Changes in Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Level 3 Inputs (Details) - Fair Value, Measurements, Recurring [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pooled Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 875	$ 707
Unrealized adjustment to fair value	(105)	158
(Premium amortization) discount accretion		0
Balance, end of period	770	865
Single-issuer Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	2,400	3,050
Unrealized adjustment to fair value	30	42
(Premium amortization) discount accretion		3
Balance, end of period	2,430	3,095
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	102,994	98,668
Unrealized adjustment to fair value	(184)	4,381
(Premium amortization) discount accretion		0
Balance, end of period	$ 102,810	$ 103,049