Debt (Details Textual) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Debt (Textual) [Abstract]
Expiry date of bank credit facility	Oct. 06, 2015
FHLB common stock amount equal rate	5.00%
Senior Notes 2015 [Member]
Debt (Textual) [Abstract]
Senior Notes	6.05%
Senior Notes 2015 [Member] | Senior Note 6.05 % [Member]
Debt (Textual) [Abstract]
Unaccrued discount	$ 51	$ 65
Aggregate principal amount	75,000
Maturity date of Senior note	Jun. 15, 2015
Imputed rate	6.10%
Senior Notes 2016 [Member]
Debt (Textual) [Abstract]
Senior Notes	6.85%
Senior Notes 2016 [Member] | Senior Note 6.85 % [Member]
Debt (Textual) [Abstract]
Unaccrued discount	107	126
Aggregate principal amount	$ 125,000
Maturity date of Senior note	Apr. 15, 2016
Imputed rate	6.90%