Income Per Share (Details Textual)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Additional Income Per Share (Textual) [Abstract]
Effect of dilutive stock-based compensation awards		839,000
Shares that may be issued upon conversion spread		3,079,000
Initial strike price under warrant	32.70
Approximate number of common stock share which can be purchased under warrants	13,200,000
Effect of potentially issuable shares under these warrants	0	1,052,000
Convertible Notes Payable [Member]
Income Per Share (Textual) [Abstract]
Interest rate of Senior Notes	3.75%
Antidilutive Securities Three Months [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stock-based compensation awards outstanding	1,576,000	884,000