Basic and Diluted Earnings Per Share - Numerator and Denominator of the Basic and Diluted Per Share Computations for Earnings Attributable to Shareholders Per Share (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified

3 Months Ended

12 Months Ended

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Net Earnings Attributable to Shareholders

Basic earnings attributable to shareholders

$ 376,888us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic

$ 348,526us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic

$ 333,360us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic

Diluted earnings attributable to shareholders

$ 376,888us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted

$ 348,526us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted

$ 333,360us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted

Weighted Average Shares

Weighted average basic shares outstanding

196,146,676us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

205,994,656us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

210,422,945us-gaap_WeightedAverageNumberOfSharesOutstandingBasic

Effect of dilutive potential common shares

621,391us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment

900,817us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment

1,512,226us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment

Weighted average diluted shares outstanding

196,768,067us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding

206,895,473us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding

211,935,171us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding

Earnings Per Share

Basic earnings attributable to shareholders per share

$ 0.52us-gaap_EarningsPerShareBasic

$ 0.53us-gaap_EarningsPerShareBasic

$ 0.46us-gaap_EarningsPerShareBasic

$ 0.42us-gaap_EarningsPerShareBasic

$ 0.41us-gaap_EarningsPerShareBasic

$ 0.45us-gaap_EarningsPerShareBasic

$ 0.39us-gaap_EarningsPerShareBasic

$ 1.92us-gaap_EarningsPerShareBasic

$ 1.69us-gaap_EarningsPerShareBasic

$ 1.58us-gaap_EarningsPerShareBasic

Diluted earnings attributable to shareholders per share

$ 0.51us-gaap_EarningsPerShareDiluted

$ 0.53us-gaap_EarningsPerShareDiluted

$ 0.46us-gaap_EarningsPerShareDiluted

$ 0.42us-gaap_EarningsPerShareDiluted

$ 0.41us-gaap_EarningsPerShareDiluted

$ 0.45us-gaap_EarningsPerShareDiluted

$ 0.39us-gaap_EarningsPerShareDiluted

$ 1.92us-gaap_EarningsPerShareDiluted

$ 1.68us-gaap_EarningsPerShareDiluted

$ 1.57us-gaap_EarningsPerShareDiluted

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The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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