Fair Value Measurement (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Fair Value Measurement [Line Items]
Percentage of unadjusted fair values obtained	98.00%
Percentage of specific unadjusted broker quotes obtained	2.00%
Transfers between Levels 1, 2, and 3 of the fair value hierarchy	$ 0	$ 0
Minimum [Member]
Fair Value Measurement [Line Items]
Number of knowledgeable outside security brokers consulted to determine fair value	1