Share-Based Compensation (Narrative) (Details) (USD $)	3 Months Ended				3 Months Ended						1 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2012 Stock Options [Member]	Mar. 31, 2011 Stock Options [Member]	Mar. 31, 2012 Restricted Stock And Restricted Stock Unit Grants [Member]	Mar. 31, 2012 Restricted Stock [Member]	Mar. 31, 2012 Restricted Stock Units [Member]	Mar. 31, 2011 Restricted Stock Units [Member]	Mar. 31, 2012 Cash-Settled Restricted Stock Units [Member]	Mar. 31, 2011 Cash-Settled Restricted Stock Units [Member]	Mar. 31, 2012 Employee Stock Purchase Program [Member]	Jan. 31, 2011 Chief Executive Officer Specific Share-Based Compensation [Member]	Mar. 31, 2012 Chief Executive Officer Specific Share-Based Compensation [Member]	Mar. 31, 2012 CAGR Of 4% [Member]	Mar. 31, 2012 CAGR Of 20% Or More [Member]	Mar. 31, 2012 Cliff Vesting [Member] Restricted Stock Grants [Member]	Mar. 31, 2012 Maximum [Member] Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, vesting period in years					4 years	4 years		4 years				3 years			3 years	10 years
Number of shares of common stock available for future grants		4,300,000		200,000						700,000
Number of distinct populations of optionees	3
Compensation cost of non-vested stock granted to employees, not yet recognized		$ 8,700,000				$ 9,100,000		$ 7,200,000
Recognition period of compensation cost of non-vested stock granted, years		2.6				3.0		3.2
Fair market value discount on common stock to eligible employees										5.00%
Shares reserved for sale to employees										1,000,000
Chief executive officer specific share-based compensation, incentive compensation award amount lower range													2,000,000
CAGR, lower range														4.00%
Chief executive officer specific share-based compensation, incentive compensation award amount higher range														9,000,000
CAGR, higher range														20.00%
Share-based compensation expense recognized		1,032,000	1,492,000			1,272,000	1,675,000	842,000	753,000			770,000
Total grant date economic value of restricted stock granted to Chief Executive Officer											$ 1,850,000