Derivative Instruments (Financial Information Related To Cash Flow Hedges) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Derivative [Line Items]
Net unrealized gains (losses) deferred in other comprehensive income, Gross	$ 7,355	$ (1,523)
Net unrealized gains (losses) deferred in other comprehensive income, Income tax expense (benefit)	2,096	(573)
Net unrealized gains (losses) deferred in other comprehensive income, Net	5,259	(950)
Cash Flow Hedge [Member]
Derivative [Line Items]
Net unrealized gains (losses) deferred in other comprehensive income, Gross	8,878	(1,522)
Net unrealized gains (losses) deferred in other comprehensive income, Income tax expense (benefit)	2,669	(573)
Net unrealized gains (losses) deferred in other comprehensive income, Net	$ 6,209	$ (949)