Income Taxes (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010 Y	Dec. 31, 2009 Y
Reconciliation of unrecognized tax benefits, excluding penalties and interest
Balance at the beginning of the period	$ 4,759,000	$ 4,857,000	$ 3,332,000
Increases during the year:
Gross increases - tax positions in prior period	1,684,000	189,000	1,071,000
Gross increases - current-period tax positions	1,844,000	981,000	636,000
Decreases during the year:
Gross decreases - tax positions in prior period	(183,000)	(490,000)	(7,000)
Decreases due to settlements with taxing authorities		(629,000)	(1,000)
Decreases due to lapse of statute of limitations	(637,000)	(149,000)	(174,000)
Balance at the end of the period	7,467,000	4,759,000	4,857,000
Number of open tax years settled (in years)		9	3
Estimated decrease in unrecognized tax benefits within the next 12-month period, low end of range	500,000
Estimated decrease in unrecognized tax benefits within the next 12-month period, high end of range	2,800,000
Estimated decrease in unrecognized tax benefits net of federal benefits within the next 12-month period, low end of range	300,000
Estimated decrease in unrecognized tax benefits net of federal benefits within the next 12-month period, high end of range	$ 1,900,000