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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pooled Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 875	$ 422	$ 707	$ 422
Realized adjustment to fair value	0
Unrealized adjustment to fair value	0	0	168	0
Settlements - calls	0		0
(Premium amortization) discount accretion	0	0	0	0
Balance, end of period	875	422	875	422
Single-issuer Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	3,200	2,775	3,050	2,450
Realized adjustment to fair value	71		71
Unrealized adjustment to fair value	153	(28)	297	291
Settlements - calls	950		950
(Premium amortization) discount accretion	1	3	7	9
Balance, end of period	2,475	2,750	2,475	2,750
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	103,122	97,923	98,668	97,256
Realized adjustment to fair value	0
Unrealized adjustment to fair value	11	233	4,465	705
Settlements - calls	0		0
(Premium amortization) discount accretion	0	0	0	195
Balance, end of period	$ 103,133	$ 98,156	$ 103,133	$ 98,156