Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Treasury Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income/(Loss)	Class A Common Stock	Class A Common Stock Common Stock
Beginning Balance (in shares) at Dec. 31, 2012							99,336
Beginning Balance at Dec. 31, 2012	$ 882,039	$ (423,900)	$ 810,094	$ 492,687	$ 3,047		$ 111
Increase (Decrease) in Stockholders' Equity
Comprehensive income	263,929			265,021	(1,092)
Purchase of treasury stock (in shares)							(6,547)
Purchase of treasury stock	(309,255)	(309,255)
Dividends declared	(57,600)			(57,600)
Exercise of stock options (in shares)							1,222
Exercise of stock options	14,589		14,588				$ 1
Restricted stock awards							83
Minimum tax withholding requirements (in shares)							(22)
Minimum tax withholding requirements	(1,327)		(1,327)
Excess tax benefit from stock-based compensation	15,369		15,369
Stock-based compensation	7,835		7,835
Ending Balance (in shares) at Dec. 31, 2013							94,072
Ending Balance at Dec. 31, 2013	815,579	(733,155)	846,559	700,108	1,955		$ 112
Increase (Decrease) in Stockholders' Equity
Comprehensive income	250,088			255,872	(5,784)
Purchase of treasury stock (in shares)							(6,671)
Purchase of treasury stock	(283,226)	(283,226)
Dividends declared	(57,406)			(57,406)
Exercise of stock options (in shares)							970
Exercise of stock options	22,171		22,170				$ 1
Restricted stock awards							(18)
Minimum tax withholding requirements (in shares)							(18)
Minimum tax withholding requirements	(762)		(762)
Excess tax benefit from stock-based compensation	3,743		3,743
Stock-based compensation	5,856		5,856
Ending Balance (in shares) at Dec. 31, 2014						88,335	88,335
Ending Balance at Dec. 31, 2014	756,043	(1,016,381)	877,566	898,574	(3,829)		$ 113
Increase (Decrease) in Stockholders' Equity
Comprehensive income	213,479			219,299	(5,820)
Purchase of treasury stock (in shares)							(12,414)
Purchase of treasury stock	(479,799)	(479,799)
Dividends declared	(59,725)			(59,725)
Exercise of stock options (in shares)							80
Exercise of stock options	1,744		1,743				$ 1
Restricted stock awards							290
Minimum tax withholding requirements (in shares)							(15)
Minimum tax withholding requirements	(574)		(574)
Excess tax benefit from stock-based compensation	604		604
Stock-based compensation	6,280		6,280
Issuance of convertible senior notes, net	30,509		30,509
Ending Balance (in shares) at Dec. 31, 2015						76,276	76,276
Ending Balance at Dec. 31, 2015	$ 468,561	$ (1,496,180)	$ 916,128	$ 1,058,148	$ (9,649)		$ 114