Convertible Debt (Details) (USD $) In Thousands, except Share data, unless otherwise specified							1 Months Ended	3 Months Ended		6 Months Ended			1 Months Ended
	Jun. 30, 2012	Dec. 31, 2011		Jun. 30, 2012 Convertible Senior Notes [Member]	Dec. 31, 2011 Convertible Senior Notes [Member]	Feb. 29, 2008 Convertible Senior Notes [Member]	Feb. 29, 2008 Convertible Senior Notes [Member] 2013 Convertible Senior Notes [Member]	Jun. 30, 2012 Convertible Senior Notes [Member] 2013 Convertible Senior Notes [Member]	Jun. 30, 2011 Convertible Senior Notes [Member] 2013 Convertible Senior Notes [Member]	Jun. 30, 2012 Convertible Senior Notes [Member] 2013 Convertible Senior Notes [Member]	Jun. 30, 2011 Convertible Senior Notes [Member] 2013 Convertible Senior Notes [Member]	Jun. 29, 2012 Convertible Senior Notes [Member] 2013 Convertible Senior Notes [Member]	Jun. 29, 2012 Convertible Senior Notes [Member] 2015 Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Debt Exchange, Principal Amount												$ 18,000	$ 18,000
Debt Instrument, Face Amount							55,000
Debt Instrument, Interest Rate, Stated Percentage							2.75%						4.50%
Debt Instrument, Convertible, Conversion Ratio							76.7448						117
Debt Instrument, Convertible, Conversion Ratio, Principal Amount							1						1
Debt Instrument, Convertible, Conversion Price						$ 13.03	$ 13.03						$ 8.53
Debt Instrument, Convertible, Difference Between Capped Call Price Per Share and Conversion Price Per Share							$ 10.055
Debt Instrument, Convertible, Conversion Price, Capped Call Price Per Share							$ 23.085
Debt Instrument, Convertible, Capped Call Transaction, Shares Delivered on Settlement Date							91,904
Debt Instrument, Convertible, Capped Call Transaction, Settlement Tranche							211,000
Debt Instrument, Capped Call Transaction, Settlement Period							20 days
Debt Instrument, Convertible, Shares Covered by Capped Call Transaction							4,200,000
Debt Instrument, Call Feature, Call Price, Percent of Principal							100.00%						100.00%
Effective interest rate								3.73%	3.64%	3.73%	3.64%
Contractually stated interest costs								309	344	618	688
Amortization of interest costs								111	112	221	224
Convertible Senior Notes, Total	45,000
Convertible senior notes, current	27,000	0	[1]
Debt Instrument, Fair Value Disclosure				$ 44,100	$ 41,800

[1] (A)As adjusted to reflect the impact of additional tax-related adjustments to the Company's purchase accounting for Continuous Computing in accordance with ASC 805-10 "Business Combinations". See Note 2 — Acquisitions for additional information.