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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pooled Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 422	$ 706	$ 422	$ 706
Unrealized adjustment to fair value	0	0	0	0
(Premium amortization) discount accretion	0	0	0	0
Balance, end of period	422	706	422	706
Single-issuer Trust Preferred Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	2,775	2,425	2,450	2,630
Unrealized adjustment to fair value	(28)	7	291	(204)
(Premium amortization) discount accretion	3	3	9	9
Balance, end of period	2,750	2,435	2,750	2,435
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	97,923	97,886	97,256	98,059
Unrealized adjustment to fair value	233	(318)	705	(668)
(Premium amortization) discount accretion	0	158	195	335
Balance, end of period	$ 98,156	$ 97,726	$ 98,156	$ 97,726