CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Earnings [Member]
Balance, beginning of year at Dec. 31, 2009		$ 3	$ 226,410	$ (11,249)
Balance, beginning of year at Dec. 31, 2009		25,909,000
Common stock (par value)
Common stock repurchased and retired		0		0
Issuance of common stock in connection with acquisition and upon exercise of options and vesting of restricted stock units		0
Additional paid-in capital
Issuance of common stock upon exercise of options and vesting of restricted stock units			14,703
Stock based compensation, net of estimated forfeiture			16,640
Issuance of common stock in connection with acquisition			0
Tax benefit of stock options	5,973		5,973
Accumulated earnings (deficit)
Common stock repurchased and retired		0		0
Net income	17,127			17,127
Total stockholders' equity	269,607
Common stock
Issuance of common stock upon exercise of options and vesting of restricted stock units		2,048,000
Common stock repurchased and retired	0
Issuance of common stock in connection with acquisition		0
Balance, end of year at Dec. 31, 2010		3	263,726	5,878
Balance, end of year at Dec. 31, 2010		27,957,000
Common stock (par value)
Common stock repurchased and retired		0		0
Issuance of common stock in connection with acquisition and upon exercise of options and vesting of restricted stock units		1
Additional paid-in capital
Issuance of common stock upon exercise of options and vesting of restricted stock units			22,277
Stock based compensation, net of estimated forfeiture			34,351
Issuance of common stock in connection with acquisition			260,322
Tax benefit of stock options	8,391		8,391
Accumulated earnings (deficit)
Common stock repurchased and retired		0		0
Net income	14,048			14,048
Total stockholders' equity	608,997
Common stock
Issuance of common stock upon exercise of options and vesting of restricted stock units		2,882,000
Common stock repurchased and retired	0
Issuance of common stock in connection with acquisition		4,000,000
Balance, end of year at Dec. 31, 2011		4	589,067	19,926
Balance, end of year at Dec. 31, 2011	34,839,000	34,839,000
Common stock (par value)
Common stock repurchased and retired		(1)		(3,752)
Issuance of common stock in connection with acquisition and upon exercise of options and vesting of restricted stock units		1
Additional paid-in capital
Issuance of common stock upon exercise of options and vesting of restricted stock units			10,210
Stock based compensation, net of estimated forfeiture			38,214
Issuance of common stock in connection with acquisition			0
Tax benefit of stock options	14,619		14,619
Accumulated earnings (deficit)
Common stock repurchased and retired		(1)		(3,752)
Net income	22,998			22,998
Total stockholders' equity	691,286
Common stock
Issuance of common stock upon exercise of options and vesting of restricted stock units		1,656,000
Common stock repurchased and retired		(137,000)
Issuance of common stock in connection with acquisition		0
Balance, end of year at Dec. 31, 2012		$ 4	$ 652,110	$ 39,172
Balance, end of year at Dec. 31, 2012	36,358,000	36,358,000