Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Total	Class A Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2011	$ 776,925us-gaap_StockholdersEquity	$ 722	$ 131,422	$ (596,622)	$ 1,245,616	$ (4,213)
Repurchase of Class A Common Stock	(54,373)			(54,373)
Issuance of treasury shares upon exercise of stock options, purchases under stock purchase plan and grants of restricted stock awards	3,361		(6,196)	9,557
Additional tax benefit resulting from exercise of options	(430)		(430)
Equity-based compensation	14,727		14,727
Net income	122,904us-gaap_NetIncomeLoss				122,904
Unrealized holding gain (loss) on investments (net of income taxes)	887					887
Unrealized holding gain anticipated sales hedging transactions (net of income taxes)	(7,241)					(7,241)
Unrealized holding gain (loss) on forward interest rate swaps hedging transactions (net of income taxes)	0
Foreign currency translation adjustment	242					242
Ending Balance at Dec. 31, 2012	857,002us-gaap_StockholdersEquity	722	139,523	(641,438)	1,368,520	(10,325)
Repurchase of Class A Common Stock	(63,102)			(63,102)
Issuance of treasury shares upon exercise of stock options, purchases under stock purchase plan and grants of restricted stock awards	14,652		(11,432)	26,084
Additional tax benefit resulting from exercise of options	2,095		2,095
Equity-based compensation	13,109		13,109
Net income	134,358us-gaap_NetIncomeLoss				134,358
Unrealized holding gain (loss) on investments (net of income taxes)	(456)					(456)
Unrealized holding gain anticipated sales hedging transactions (net of income taxes)	118					118
Unrealized holding gain (loss) on forward interest rate swaps hedging transactions (net of income taxes)	0
Foreign currency translation adjustment	882					882
Ending Balance at Dec. 31, 2013	958,658us-gaap_StockholdersEquity	722	143,295	(678,456)	1,502,878	(9,781)
Issuance of treasury shares upon exercise of stock options, purchases under stock purchase plan and grants of restricted stock awards	21,725		(22,067)	43,792
Additional tax benefit resulting from exercise of options	5,971		5,971
Equity-based compensation	19,891		19,891
Net income	32,429us-gaap_NetIncomeLoss				32,429
Unrealized holding gain (loss) on investments (net of income taxes)	425					425
Unrealized holding gain anticipated sales hedging transactions (net of income taxes)	7,190					7,190
Unrealized holding gain (loss) on forward interest rate swaps hedging transactions (net of income taxes)	(7,699)					(7,699)
Foreign currency translation adjustment	1,318					1,318
Ending Balance at Dec. 31, 2014	$ 1,039,908us-gaap_StockholdersEquity	$ 722	$ 147,090	$ (634,664)	$ 1,535,307	$ (8,547)

This element represents the amount of recognized equity-based compensation during the period, that is, the amount recognized as expense in the income statement (or as asset if compensation is capitalized). Alternate captions include the words "stock-based compensation".

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Amount of increase in additional paid in capital (APIC) resulting from a tax benefit associated with share-based compensation plan other than an employee stock ownership plan (ESOP). Includes, but is not limited to, excess tax benefit.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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