Share-Based Compensation (Narrative) (Details) (USD $)	6 Months Ended	3 Months Ended		6 Months Ended			6 Months Ended			3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			1 Months Ended	6 Months Ended
	Jun. 30, 2012 optionee_population	Jun. 30, 2012 Stock Options [Member]	Jun. 30, 2011 Stock Options [Member]	Jun. 30, 2012 Stock Options [Member] Y	Jun. 30, 2011 Stock Options [Member]	May 17, 2012 Stock Options [Member]	Jun. 30, 2012 Stock Option and Stock Appreciation Right [Member]	Jun. 30, 2012 Other [Member]	Jun. 30, 2012 Restricted Stock [Member]	Jun. 30, 2012 Restricted Stock Units [Member]	Jun. 30, 2011 Restricted Stock Units [Member]	Jun. 30, 2012 Restricted Stock Units [Member] Y	Jun. 30, 2011 Restricted Stock Units [Member]	Jun. 30, 2012 Cash-Settled Restricted Stock Units [Member]	Jun. 30, 2011 Cash-Settled Restricted Stock Units [Member]	Jun. 30, 2012 Cash-Settled Restricted Stock Units [Member] Y	Jun. 30, 2011 Cash-Settled Restricted Stock Units [Member]	Jun. 30, 2012 Employee Stock Purchase Program [Member]	Jan. 31, 2011 Chief Executive Officer Specific Share-Based Compensation [Member]	Jun. 30, 2012 Chief Executive Officer Specific Share-Based Compensation [Member]	Jun. 30, 2012 CAGR Of 4% [Member]	Jun. 30, 2012 CAGR Of 20% Or More [Member]	Jun. 30, 2012 Cliff Vesting [Member] Restricted Stock Grants [Member]	Jun. 30, 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				4 years				3 years			3 years	10 years
Number of shares of common stock available for future grants		6,500,000		6,500,000		6,500,000												700,000
Share-based Compensation Arranagement by Share-based Payment Award, Number of Shares against Plan							1	1.75
Number of distinct populations of optionees	3
Compensation cost of non-vested stock granted to employees, not yet recognized		$ 7,600,000		$ 7,600,000						$ 8,200,000		$ 8,200,000		$ 6,500,000		$ 6,500,000
Recognition period of compensation cost of non-vested stock granted, years				2.6								2.6				3.0
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		968,000	1,011,000	2,000,000	2,503,000					1,180,000	1,405,000	2,452,000	3,080,000	480,000	285,000	1,322,000	1,038,000			749,000
Total grant date economic value of restricted stock granted to Chief Executive Officer																			$ 1,850,000