Accounting for Stock-Based Compensation (Details) - USD ($) $ in Thousands, shares in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Stock-based compensation activity, including both continuing and discontinued operations
Stock-based compensation expense recognized in operating expenses	$ 3,373	$ 2,991	$ 5,853		$ 6,075
Less: Tax benefit of stock-based compensation expense in provision for income taxes	1,204	1,082	2,122		2,139
Stock-based compensation expense, net of tax	2,169	1,909	3,731		3,936
Fair value of shares vested	3,601	3,211	5,951		5,995
Proceeds to the Company from the exercise of stock-based compensation	1,512	92	2,525		5,576
Tax effect from the exercise of stock-based compensation, including shortfall tax benefits	5	(2)	19	$ (132)	(186)
Fair value of financial instruments
United States Treasury securities and money market funds	$ 35,043	$ 92,875	$ 35,043	$ 76,047	$ 92,875
Income Taxes
Effective tax rate (as a percent)	35.80%	38.50%	36.70%		38.40%
Provision for income taxes	$ 14,640	$ 13,446	$ 24,703		$ 19,637
Stock Compensation Plan
Stock-based compensation activity, including both continuing and discontinued operations
Stock-based compensation cost capitalized in inventory	$ 480	$ 500	$ 480		$ 500
2011 Plan
Stock-Based Compensation
Maximum common stock shares that may be issued under plan	16.3		16.3

Represents the amount of investment made by the entity in United States Treasury securities and money market funds.

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Amount of increase (decrease) in additional paid in capital (APIC) resulting from a tax benefit (deficiency) associated with an share-based compensation plan other than an employee stock ownership plan (ESOP).

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

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-Publisher FASB
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The amount of expense, net of income tax, recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Gross amount of an expenditure that is incurred which is not expensed in the current period but rather capitalized as a component of inventory.

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The cash inflow associated with the amount received from holders exercising their stock options. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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