Fair Value Measurements - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair Value Measurements Of Financial Instruments [Line Items]
Marketable Securities, Unrealized Gain (Loss)	$ 12,078,000	$ (12,124,000)	$ 4,884,000
Fair value of related party assets	12,900,000
Carrying value of related party assets	5,800,000	6,700,000
Inventories with carrying value	3,800,000	54,600,000
Minimum [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Short-term maturities	15 days
Maximum [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Short-term maturities	40 days
Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Mortgage loans held-for-sale	119,953,000	78,335,000
Not Under Commitment To Sell [Member] | Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Mortgage loans held-for-sale	11,700,000	800,000
Under Commitment To Sell [Member] | Mutual Fund [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Marketable Securities, Unrealized Gain (Loss)	4.8	7.2
Held-to-maturity Securities, Transferred to Trading Securities, Unrealized Gain (Loss)	2.1	6.5
Number of Mutual Fund	4
Under Commitment To Sell [Member] | Level 2 [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Mortgage loans held-for-sale	$ 108,300,000	$ 77,500,000