Financial Information (Schedule of Accounting Changes) (Details) - USD ($)	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
New Accounting Pronouncement or Change in
Other Assets	$ 1,392,160,000	$ 1,436,291,000	$ 1,416,635,000
Term borrowings	$ 1,323,749,000	1,312,677,000	1,570,646,000
Accounting Standards Update 201503 [Member]
New Accounting Pronouncement or Change in
Other Assets		(2,499,000)	(2,569,000)	$ (2,764,000)
Term borrowings		$ (2,499,000)	$ (2,569,000)	$ (2,764,000)