Fair Value of Financial Instruments (Fair Value of Financial Instruments, Classified Using Three-Level Hierarchy) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 1,041,259	$ 834,837
Accounts and accrued income receivable, net	291,607	236,895
Loans receivable, net	60,223	73,397
Deposits with banks	24,204	23,601
Available-for-sale investments at fair value	3,260,493	3,177,860
Notes receivable, net	9,927	9,953
Deposits	1,962,839	1,693,138
Accounts payable and accrued liabilities	361,730	406,819
Notes and contracts payable	458,571	301,007
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents	1,041,259	834,837
Accounts and accrued income receivable, net	291,607	236,895
Deposits with banks	3,046	2,070
Available-for-sale investments at fair value	313,289	358,043
Deposits	1,943,463	1,666,336
Accounts payable and accrued liabilities	361,730	406,819
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Deposits with banks	21,158	21,531
Available-for-sale investments at fair value	2,929,210	2,800,795
Deposits	19,376	26,802
Notes and contracts payable	448,090	294,221
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans receivable, net	60,223	73,397
Available-for-sale investments at fair value	17,994	19,022
Notes receivable, net	9,927	9,953
Notes and contracts payable	10,481	6,786
Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale investments at fair value	2,947,204	2,819,817
Debt Securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale investments at fair value	2,929,210	2,800,795
Debt Securities | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale investments at fair value	17,994	19,022
Equity Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale investments at fair value	313,289	358,043
Equity Securities | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale investments at fair value	$ 313,289	$ 358,043