Stock-Based Compensation Plans (Narrative) (Details) (USD $)	3 Months Ended			3 Months Ended			3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 Maximum Potential Issuances Based On Grants To Date [Member]	Mar. 31, 2012 2007 Plan [Member]	May 31, 2011 2007 Plan [Member]	May 31, 2009 2007 Plan [Member]	Mar. 31, 2012 1997 Plan [Member]	Mar. 31, 2012 Executive Officer [Member]	Mar. 31, 2011 Executive Officer [Member]	Mar. 31, 2012 Long-Term Incentive Program Awards [Member]	Mar. 31, 2012 Minimum [Member] Long-Term Incentive Program Awards [Member]	Mar. 31, 2012 Maximum [Member] Long-Term Incentive Program Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares approved for issuance				500,000
Shares additionally approved for issuance					2,860,000	325,000
Shares available for future grants				1,339,702
Compensation cost charged to income for stock options	$ 2,300,000	$ 1,100,000
Percentage of performance based award payouts											0.00%	200.00%
Share based payment award options term				7 years			10 years			7 years
Award vesting period, minimum, years	one			three						three
Award vesting period, maximum, years	five			five
Weighted average grant date fair value per share of options granted								$ 14.91	$ 16.34
Aggregate intrinsic value of options exercised	$ 4,500,000	$ 625,000
Maximum number of performance-vested shares that could be issued			426,262