Condensed Financial Information of Parent Company - Condensed Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets
Other assets, net	$ 25,201us-gaap_OtherAssets	$ 20,924us-gaap_OtherAssets
Total assets	7,377,920us-gaap_Assets	6,664,967us-gaap_Assets	6,363,364us-gaap_Assets
Liabilities	6,499,811us-gaap_Liabilities	5,893,080us-gaap_Liabilities
Stockholders' equity	878,109us-gaap_StockholdersEquity	771,887us-gaap_StockholdersEquity	762,970us-gaap_StockholdersEquity	714,814us-gaap_StockholdersEquity
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	7,377,920	6,664,967
Parent Company [Member]
Assets
Investment in subsidiaries	895,972	789,448
Other assets, net	19,069	19,120
Total assets	915,041	808,568
Liabilities	36,932	36,681
Stockholders' equity	878,109	771,887
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 915,041	$ 808,568

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

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Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.

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Amount of liabilities and equity items, including the portion of equity attributable to noncontrolling interests, if any.

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The aggregate carrying amounts, as of the balance sheet date, of assets not separately disclosed in the balance sheet.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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