Stock Compensation Plans (Details 3) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011
Summary of stock compensation awards outstanding and exercisable
Number of Awards outstanding, Ending balance (in shares)	1,714,113
Weighted Average Exercise Price Awards outstanding, Ending balance (in dollars per share)	$ 24.41
Intrinsic Value Awards outstanding, Ending balance	$ 6,362
Weighted Average Remaining Contractual Life Awards outstanding, Ending balance	5 years 5 months 1 day
Number of Awards exercisable, Ending balance (in shares)	1,054,054
Weighted Average Exercise Price Awards exercisable, Ending balance (in dollars per share)	$ 23.37
Intrinsic Value Awards exercisable, Ending balance	$ 4,495
Weighted Average Remaining Contractual Life Awards exercisable, Ending balance	3 years 5 months 23 days