Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Provision for income taxes
Current	$ 4,886	$ 5,741	$ 8,754
Deferred	23,204	25,715	13,817
Provision for income taxes	$ 28,090	$ 31,456	$ 22,571