Accumulated Other Comprehensive Income (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2014	$ 3,241
Unrealized gains (losses)	1,932
Amounts reclassified from AOCI	1,672
Balance at March 31, 2015	6,845
Derivative Instruments [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2014	2,550
Unrealized gains (losses)	3,535
Amounts reclassified from AOCI	(307)
Balance at March 31, 2015	5,778
Pension, Postretirement and Other Postemployment Benefits [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2014	2,860
Unrealized gains (losses)	0
Amounts reclassified from AOCI	189
Balance at March 31, 2015	3,049
Available-for-Sale Securities [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2014	(2,169)
Unrealized gains (losses)	(1,603)
Amounts reclassified from AOCI	1,790
Balance at March 31, 2015	$ (1,982)