Income Taxes Summary of Income Tax Contingencies (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, balance January 1	$ 2,952	$ 2,790	$ 2,668
Gross increases in tax positions taken in a prior year	347	518	163
Gross decreases in tax positions taken in a prior year	0	(51)	(40)
Gross increases in tax positions taken in the current year	865	520	710
Settlements with taxing authorities	(507)	0	0
Lapse of applicable statute of limitations	(544)	(825)	(711)
Unrecognized tax benefits, balance December 31	$ 3,113	$ 2,952	$ 2,790