Earnings Per Common Share Data (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share Disclosure [Line Items]
Net earnings	$ 27,713	$ 36,740	$ 76,168	$ 84,868
Distributed Earnings	(11,912)	0	(35,632)	0
Undistributed Earnings, Basic	15,801	36,740	40,536	84,868
Percentage of Undistributed Earnings Allocated to Common Shares	98.30%	100.00%	98.30%	100.00%
Undistributed Earnings Allocated to Common Shares	15,532	36,740	39,847	84,868
Dividends, Common Stock, Cash	11,714	0	35,028	0
Net Income (Loss) Available to Common Stockholders	$ 27,246	$ 36,740	$ 74,875	$ 84,868
Weighted Average Number of Shares Outstanding, Basic	37,460	39,047	37,818	40,777
Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights	642	0	653	0
Weighted-average common shares outstanding, diluted	38,684	40,832	39,147	42,532
Earnings Per Share, Basic	$ 0.73	$ 0.94	$ 1.98	$ 2.08
Net earnings per common share, diluted	$ 0.70	$ 0.90	$ 1.91	$ 2.00
Incremental Common Shares Attributable to Share-based Payment Arrangements	1,224	1,785	1,329	1,755
Weighted Average Number of Shares Outstanding, Total	38,102	39,047	38,471	40,777
Anti-dilutive options excluded from calculation of weighted-average common shares outstanding, diluted	2,560	3,184	2,611	3,397

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Antidilution

-URI http://asc.fasb.org/extlink&oid=6505113

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Diluted Earnings Per Share

-URI http://asc.fasb.org/extlink&oid=6510752

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Contingent Stock Agreement

-URI http://asc.fasb.org/extlink&oid=6508534

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 128

-Paragraph 40

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 128

-Paragraph 13, 14

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 07-4

-Paragraph 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 128

-Paragraph 171

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.