Fair Value Measurement (Narrative) (Details)	6 Months Ended
	Jun. 30, 2016 transfers broker	Jun. 30, 2015 transfers
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percentage of portfolio of unadjusted fair values obtained	99.70%
Percentage of portfolio of specific unadjusted broker quotes obtained	0.30%
Transfers between Levels 1, 2, and 3 of the fair value hierarchy | transfers	0	0
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of knowledgeable outside security brokers consulted to determine fair value | broker	1