Nontrade Receivables and Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Nontrade receivables	$ 10,482,229	$ 8,900,316
Allowance for credit losses	(53,276)	(42,925)	$ (41,486)
Net nontrade receivables	10,428,953	8,857,391
Non Trade Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Nontrade receivables	32,823	30,557
Allowance for credit losses	(4,876)	(5,525)	$ (6,486)
Net nontrade receivables	27,947	25,032
Agents \| Non Trade Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Nontrade receivables	11,860	6,976
Allowance for credit losses	(4,876)	(5,525)
Net nontrade receivables	6,984	1,451
Reinsurer \| Non Trade Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Nontrade receivables	20,963	23,581
Net nontrade receivables	$ 20,963	$ 23,581

A valuation allowance for financing receivables that are expected to be uncollectible.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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+ References

No definition available.

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- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

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- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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