Stockholders' Equity (Stock Option Plan Activity) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended	12 Months Ended
Jun. 30, 2014	Dec. 31, 2013
Shares
Balance, Beginning	1,746,709
Granted	366,184
Exercised	(233,929)
Forfeited	(49,967)
Cancelled	(3,814)
Balance, Ending	1,825,183	1,746,709
Exercisable	945,222
Options vested and expected to vest	1,825,183
Weighted Average Exercise Price
Balance, Beginning	$ 16.79
Granted (in usd per share)	$ 73.81
Exercised (in usd per share)	$ 15.72
Forfeited (in usd per share)	$ 16.69
Cancelled (in usd per share)	$ 84.38
Balance, Ending	$ 28.23	$ 16.79
Exercisable	$ 16.30
Options vested and expected to vest	$ 28.23
Weighted-Average Remaining Contractual Term in Years
Weighted average remaining contractual term in years	7 years 8 months 12 days	7 years 6 months 26 days
Exercisable	6 years 9 months 11 days
Options vested and expected to vest	7 years 8 months 12 days
Aggregate Intrinsic Value
Aggregate intrinsic value	$ 66,386	$ 62,705
Exercisable	43,474
Options vested and expected to vest	$ 66,386

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of fully vested and expected to vest options outstanding.

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