CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Retained Earnings	Non-controlling interest in subsidiaries
Beginning Balance at Dec. 31, 2012	$ 817,931	$ 426	$ 162,470	$ 37,379	$ (112,655)	$ 730,311	$ 0
Beginning Balance (in shares) at Dec. 31, 2012		38,908
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued upon exercise of stock options (in shares)		70
Stock issued upon exercise of stock options	1,672	1	1,671
Tax benefit from stock option and restricted stock units	6,509		6,509
Stock issued upon vesting of restricted and deferred stock units (in shares)		241
Stock issued upon vesting of restricted and deferred stock units	0	2	(2)
Stock-based compensation, net of share repurchases for tax withholdings	(4,033)		(4,033)
Purchase of shares of treasury stock, Shares		0
Purchase of shares of treasury stock	(17,911)				(17,911)
Changes in available-for-sale securities, net of tax effect of $116 in 2014 and $(289) in 2013	(492)			(492)
Foreign currency translation	(36,550)			(36,550)			0
Net income (loss)	114,740					114,740	0
Ending Balance at Sep. 30, 2013	881,866	429	166,615	337	(130,566)	845,051	0
Ending Balance (in shares) at Sep. 30, 2013		39,219
Beginning Balance at Dec. 31, 2013	903,297	429	168,891	(15,495)	(130,566)	879,519	519
Beginning Balance (in shares) at Dec. 31, 2013		38,987
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued upon exercise of stock options (in shares)		17
Stock issued upon exercise of stock options	236	0	236
Tax benefit from stock option and restricted stock units	1,432		1,432
Stock issued upon vesting of restricted and deferred stock units (in shares)		77
Stock issued upon vesting of restricted and deferred stock units	0	1	(1)
Stock-based compensation, net of share repurchases for tax withholdings	6,747		6,747
Purchase of shares of treasury stock, Shares		(211)
Purchase of shares of treasury stock	(19,765)				(19,765)
Changes in available-for-sale securities, net of tax effect of $116 in 2014 and $(289) in 2013	200			200
Foreign currency translation	(10,455)			(9,448)			(1,007)
Non-controlling interest investment	21,267						21,267
Net income (loss)	152,810					154,318	(1,508)
Ending Balance at Sep. 30, 2014	$ 1,055,769	$ 430	$ 177,305	$ (24,743)	$ (150,331)	$ 1,033,837	$ 19,271
Ending Balance (in shares) at Sep. 30, 2014		38,870