Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Held-to-maturity Securities [Line Items]
Carrying value	$ 9,500		$ 9,500		$ 79,787
Cost or amortized cost	9,500		9,500		79,787
Fair value	9,500		9,500		79,794
Schedule of Trading Securities and Other Trading Assets [Line Items]
Carrying Value	0		0		0
Cost or amortized cost	0	83	0	83	0
Fair Value	0	77	0	77	0
Gross unrealized gains (losses) on investment securities held to maturity [Abstract]
Gross unrealized gains (losses)			0		7
Unrealized gains (losses) on investment securities [Abstract]
Cost basis	0	83	0	83	0
Current value	0	77	0	77	0
Unrealized gains (losses)	0	(6)	0	(6)
Realized gains (losses) on investment securities [Abstract]
Net sale proceeds	4	272	6	505
Cost basis	0	(263)	0	(480)
Realized gains (losses)	4	9	6	25
US Treasury Bills [Member]
Held-to-maturity Securities [Line Items]
Carrying value	9,500		9,500		79,787
Cost or amortized cost	9,500		9,500		79,787
Fair value	$ 9,500		$ 9,500		$ 79,794