Income Taxes - Additional Information (Detail)	12 Months Ended
Dec. 31, 2015 USD ($) State	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Income Tax Disclosure [Abstract]
Tax bad debt reserve	$ 137,121,000
Income taxes attributable to gains or losses on bank investment securities	0	$ 0	$ 18,313,000
Minimum alternative tax expense recognized for gains or losses on bank investment securities	$ 0	$ 0	$ 0
Number of state and local jurisdictions where company files income tax returns \| State	40

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from the allowance for doubtful accounts.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 25
-Paragraph 20
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51675352&loc=d3e28680-109314

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32632-109319

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32621-109319

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant