Earnings Per Common Share Data (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share Disclosure [Line Items]
Net earnings	$ 21,669	$ 26,421
Distributed Earnings	(12,024)	0
Undistributed Earnings, Basic	9,645	26,421
Percentage of Undistributed Earnings Allocated to Common Shares	98.30%	100.00%
Undistributed Earnings Allocated to Common Shares	9,481	26,421
Dividends, Common Stock, Cash	11,818	0
Net Income (Loss) Available to Common Stockholders	$ 21,299	$ 26,421
Weighted Average Number of Shares Outstanding, Basic	38,308	42,114
Incremental Common Shares Attributable to Participating Nonvested Shares with Non-forfeitable Dividend Rights	668	0
Weighted-average common shares outstanding, diluted	39,806	44,045
Earnings Per Share, Basic	$ 0.56	$ 0.63
Net earnings per common share, diluted	$ 0.54	$ 0.60
Incremental Common Shares Attributable to Share-based Payment Arrangements	1,498	1,931
Weighted Average Number of Shares Outstanding, Total	38,976	42,114
Anti-dilutive options excluded from calculation of weighted-average common shares outstanding, diluted	2,486	3,486

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 Emerging Issues Task Force (EITF)

-Number 07-4

-Paragraph 4

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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

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

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

-Publisher FASB

-Name Accounting Standards Codification

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

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 128

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 128

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

-Publisher FASB

-Name Accounting Standards Codification

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