Consolidated Statements of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Total USD ($)	Treasury Stock USD ($)	Paid-in-Capital USD ($)	Retained Earnings USD ($)	Accumulated Other Comprehensive Income/(Loss) USD ($)	Class A Common Stock	Class A Common Stock Common Stock USD ($)	Class B Common Stock	Class B Common Stock Common Stock USD ($)
Balance at Dec. 31, 2011	$ 978,462	$ (65,048)	$ 741,848	$ 298,831	$ 2,724		$ 105		$ 2
Balance (in shares) at Dec. 31, 2011							102,985		2,060
Increase (Decrease) in Stockholders' Equity
Comprehensive income	240,519			240,196	323
Conversion of Class B stock to Class A stock							2		(2)
Conversion of Class B stock to Class A stock (in shares)							2,060		(2,060)
Purchase of treasury stock	(358,852)	(358,852)
Purchase of treasury stock (in shares)							(9,477)
Common stock dividends $0.60 and $0.44 per share for the years ended December 31, 2013 and 2012, respectively	(45,216)			(45,216)
Conversions to common stock	63,444		63,440				4
Conversions to common stock (in shares)							3,676
Non-cash stock-based compensation	4,806		4,806
Other	(1,124)			(1,124)
Balance at Dec. 31, 2012	882,039	(423,900)	810,094	492,687	3,047		111
Balance (in shares) at Dec. 31, 2012						99,244	99,244
Balance at Dec. 31, 2010	619,483	(2,277)	451,728	171,224	(1,280)		60		28
Balance (in shares) at Dec. 31, 2010							59,199		28,169
Increase (Decrease) in Stockholders' Equity
Comprehensive income	136,337			132,333	4,004
Issuance of common stock	237,253		237,237				16
Issuance of common stock (in shares)							16,000
Conversion of Class B stock to Class A stock							26		(26)
Conversion of Class B stock to Class A stock (in shares)							26,109		(26,109)
Purchase of treasury stock	(62,771)	(62,771)
Purchase of treasury stock (in shares)							(2,235)
Preferred stock dividends	(4,726)			(4,726)
Conversions to common stock	48,954		48,951				3
Conversions to common stock (in shares)							3,912
Non-cash stock-based compensation	3,932		3,932
Balance at Dec. 31, 2011	978,462	(65,048)	741,848	298,831	2,724		105		2
Balance (in shares) at Dec. 31, 2011							102,985		2,060
Balance at Dec. 31, 2012	882,039	(423,900)	810,094	492,687	3,047		111
Balance (in shares) at Dec. 31, 2012						99,244	99,244
Increase (Decrease) in Stockholders' Equity
Comprehensive income	263,929			265,021	(1,092)
Purchase of treasury stock	(310,582)	(310,582)
Purchase of treasury stock (in shares)							(6,547)
Common stock dividends $0.60 and $0.44 per share for the years ended December 31, 2013 and 2012, respectively	(57,600)			(57,600)
Conversions to common stock	29,958		29,957				1
Conversions to common stock (in shares)							1,292
Non-cash stock-based compensation	7,835		7,835
Balance at Dec. 31, 2013	$ 815,579	$ (734,482)	$ 847,886	$ 700,108	$ 1,955		$ 112
Balance (in shares) at Dec. 31, 2013	94,000					93,989	93,989	0