On-Balance Sheet Derivative Instruments And Hedging Activities (Outstanding Interest Rate Swap Agreements) (Details) (Interest Rate Swap [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Interest Rate Swap [Member]
Outstanding Interest Rate Swap Agreements [Line Items]
Notional amount	$ 657,588	$ 568,755
Weighted average pay rate	3.80%	4.50%
Weighted average receive rate	0.30%	0.50%
Weighted average maturity in years	6.8	6.7
Unrealized gain (loss) relating to interest rate swaps	$ (2,939)	$ 14,414

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration