Net Income (Loss) per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended											12 Months Ended
	Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014		Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
(Numerator)
Net income (loss)	$ (76,166)	[1]	$ (124,212)	[2],[3]	$ (2,026)	$ (16,368)	$ (11,783)		$ 63,937	$ 26,373	$ (3,290)	$ (218,772)	$ 75,237	$ 84,009	$ 86,452
Weighted-average shares outstanding during period:
Class A and B - basic							69,408					70,071		68,411	67,100
Common stock equivalents														1,991	2,620
Class A and B - diluted							69,408					70,071		70,402	69,720
Net income (loss) per share:
Class A and B - basic							$ (0.17)	[2]	$ 0.93	$ 0.38	$ (0.05)	$ (3.12)	$ 1.09	$ 1.23	$ 1.29
Class A and B - diluted							$ (0.17)	[2]	$ 0.90	$ 0.37	$ (0.05)	$ (3.12)	$ 1.07	$ 1.19	$ 1.24
Options to purchase shares of common stock and RSUs excluded from the calculation of diluted net income per share as the effect would have been antidilutive							8,422					6,306		3,098	1,472

[1] Includes a tax benefit due to the release of valuation allowances. Refer to Note 11 - "Income Taxes" for additional information.

[2] Includes a tax provision due to the increase of valuation allowance. Refer to Note 11 - "Income Taxes" for additional information.

[3] Includes a goodwill impairment charge. Refer to Note 7 - "Goodwill" for additional information.