Debt Obligations (Proceeds Upon Issuance Of Senior Convertible Notes) (Details) (USD $)	12 Months Ended	0 Months Ended
	Dec. 31, 2011	May 10, 2011 2.625% Senior Convertible Notes Due May 15, 2041 [Member]	Dec. 31, 2011 2.625% Senior Convertible Notes Due May 15, 2041 [Member]
Debt Instrument [Line Items]
Principal value senior convertible notes		$ 700,000,000	$ 700,000,000
Less issuance cost		(15,750,000)
Net proceeds, senior convertible notes		684,250,000
Senior convertible notes		270,004,000
Common stock, net	262,367,000	262,367,000
Long-term deferred tax liability		161,043,000
Issuance costs allocated to senior convertible notes		(6,087,000)
Long-term deferred tax asset		(3,624,000)
Contingent interest derivative liability		547,000
Net proceeds, senior convertible notes		$ 684,250,000