Fair Value Measurement (Narrative) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2012 transfers	Jun. 30, 2011 transfers	Jun. 30, 2012
Fair Value Measurement [Line Items]
Percentage of portfolio of unadjusted fair values obtained			97.00%
Percentage of portfolio of specific unadjusted broker quotes obtained			3.00%
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