Restatement and Revision of Previously Issued Unaudited Financial Statements - Effect of Revisions on Affected Line Items on Condensed Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Mar. 31, 2013	Feb. 28, 2013	Dec. 31, 2012	Jun. 30, 2012	Mar. 26, 2012	Dec. 31, 2011
Condensed Consolidated Balance Sheet Data:
Cash and cash equivalents	$ 182,568	$ 206,638		$ 243,465	$ 161,198	$ 171,970	$ 223,849
Restricted cash	5,819			3,478	6,787
Accounts receivable, net	125,927			78,928	75,047
Total current assets	409,851			386,580	274,462
Deferred income taxes	45,267			57,471	36,654
Total assets	767,578		6,614	675,204	558,651
Other current liabilities	43,177		3,060	106,796	33,091
Total current liabilities	349,701			327,023	261,452
Other liabilities	43,208			82,416	63,169
Total liabilities	637,892		46,114	549,439	474,621
Capital surplus	195,141			197,113	189,267
Retained earnings	970,405			967,473	935,145
Total shareholders' equity	129,686			125,765	84,030		169,105
Total liabilities and shareholders' equity	767,578			675,204	558,651
As Previously Reported [Member]
Condensed Consolidated Balance Sheet Data:
Cash and cash equivalents	185,408			246,342	167,234
Restricted cash	776			601	751
Accounts receivable, net	123,076			77,313	73,675
Total current assets	358,179			384,965	273,090
Deferred income taxes	52,759			56,112	36,016
Total assets	629,473			672,230	556,641
Other current liabilities	41,521			86,722	19,454
Total current liabilities	245,350			306,949	247,815
Other liabilities	84,191			98,327	74,615
Total liabilities	449,541			545,276	472,430
Capital surplus	204,731			206,703	198,812
Retained earnings	1,011,061			959,072	925,781
Total shareholders' equity	179,932			126,954	84,211
Total liabilities and shareholders' equity	629,473			672,230	556,641
Revisions [Member]
Condensed Consolidated Balance Sheet Data:
Cash and cash equivalents				(2,877)	(6,036)
Restricted cash				2,877	6,036
Accounts receivable, net				1,615	1,372
Total current assets				1,615	1,372
Deferred income taxes				1,359	638
Total assets				2,974	2,010
Other current liabilities				20,074	13,637
Total current liabilities				20,074	13,637
Other liabilities				(15,911)	(11,446)
Total liabilities				4,163	2,191
Capital surplus				(9,590)	(9,545)
Retained earnings				8,401	9,364
Total shareholders' equity				(1,189)	(181)
Total liabilities and shareholders' equity				$ 2,974	$ 2,010