Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]
Beginning Balance at Dec. 31, 2011	$ 990,012us-gaap_StockholdersEquity	$ 113	$ 707,419	$ 268,870	$ 13,610
Beginning Balance, Shares at Dec. 31, 2011		52,491,948
Net issuance under stock-based plans	1,564		1,564
Net issuance under stock-based plans, Shares		691,501
Stock-based compensation	13,031		13,031
Tax effect from stock-based plans	1,862		1,862
Stock repurchase	(11,501)		(5,871)	(5,630)
Stock repurchase, Shares		(434,600)
Cash dividend	(32,686)us-gaap_DividendsCommonStockCash			(32,686)
Comprehensive income (net of tax):
Net income	48,029us-gaap_NetIncomeLoss			48,029
Other comprehensive income (loss)	1,845				1,845
Ending Balance at Dec. 31, 2012	1,012,156us-gaap_StockholdersEquity	113	718,005	278,583	15,455
Ending Balance, Shares at Dec. 31, 2012		52,748,849
Net issuance under stock-based plans	(464)		(464)
Net issuance under stock-based plans, Shares		721,601
Stock-based compensation	13,992		13,992
Tax effect from stock-based plans	495		495
Stock repurchase	(2,875)		(1,457)	(1,418)
Stock repurchase, Shares	(107,000)	(107,000)
Cash dividend	(33,975)us-gaap_DividendsCommonStockCash			(33,975)
Comprehensive income (net of tax):
Net income	35,776us-gaap_NetIncomeLoss			35,776
Other comprehensive income (loss)	(3,582)				(3,582)
Ending Balance at Dec. 31, 2013	1,021,523us-gaap_StockholdersEquity	113	730,571	278,966	11,873
Ending Balance, Shares at Dec. 31, 2013		53,363,450
Net issuance under stock-based plans	2,492		2,492
Net issuance under stock-based plans, Shares		519,128
Stock-based compensation	11,315		11,315
Tax effect from stock-based plans	331		331
Stock repurchase	(20,809)		(9,977)	(10,832)
Stock repurchase, Shares	(727,912)	(727,912)
Cash dividend	(34,851)us-gaap_DividendsCommonStockCash			(34,851)
Comprehensive income (net of tax):
Net income	115,778us-gaap_NetIncomeLoss			115,778
Other comprehensive income (loss)	(13,957)				(13,957)
Ending Balance at Dec. 31, 2014	$ 1,081,822us-gaap_StockholdersEquity	$ 113	$ 734,732	$ 349,061	$ (2,084)
Ending Balance, Shares at Dec. 31, 2014		53,154,666

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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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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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 other comprehensive income (loss).

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Number of shares of stock issued as of the balance sheet date, including shares that had been issued and were previously outstanding but which are now held in the treasury.

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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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Value of stock (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of stock value of such awards forfeited. Stock issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern 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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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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