Income Taxes (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Summary of income tax contingencies
Balance at January 1	$ 70,496	$ 65,170
Additions for tax positions taken during the current year	8,061	531
Additions for tax positions taken during a prior year	7,058	14,815
Reductions for tax positions taken during a prior year	(11,464)	(2,069)
Settlements with taxing authorities	(24,835)	(2,539)
Reductions due to lapse of applicable statute of limitations	(12,852)	(5,412)
Balance at December 31	$ 36,464	$ 70,496