Fair Value of Financial Instruments (Carrying Amounts and Fair Values of Financial Instruments) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 770,420	$ 834,837
Accounts and accrued income receivable, net	242,541	236,895
Loans receivable, net	70,733	73,397
Deposits with banks	22,832	23,601
Available-for-sale investments at fair value	3,172,274	3,177,860
Notes receivable, net	9,361	9,953
Deposits	1,762,458	1,693,138
Accounts payable and accrued liabilities	316,016	406,819
Notes and contracts payable	455,824	301,007
Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	770,420	834,837
Accounts and accrued income receivable, net	242,541	236,895
Loans receivable, net	69,479	73,755
Deposits with banks	22,754	23,492
Notes receivable, net	9,932	10,542
Deposits	1,762,117	1,692,932
Accounts payable and accrued liabilities	316,016	406,819
Notes and contracts payable	457,001	310,285
Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	770,420	834,837
Accounts and accrued income receivable, net	242,541	236,895
Loans receivable, net	70,733	73,397
Deposits with banks	22,832	23,601
Notes receivable, net	9,361	9,953
Deposits	1,762,458	1,693,138
Accounts payable and accrued liabilities	316,016	406,819
Notes and contracts payable	455,824	301,007
Debt Securities | Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale investments at fair value	2,825,477	2,819,817
Debt Securities | Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale investments at fair value	2,825,477	2,819,817
Equity Securities | Carrying Amount
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale investments at fair value	346,797	358,043
Equity Securities | Fair Value
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale investments at fair value	$ 346,797	$ 358,043