Convertible Notes and Non-recourse Notes (Convertible and Non-Recourse Notes) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Balance at beginning of period	$ 409,985	$ 514,698
Issuance and exchange	0	136,313
Payment	(93,370)	(110,900)	(95,730)
Repurchase	0	133,464
Non-cash discount	(16,833)
Discount amortization	(10,170)	(3,338)
Balance at ending of period	309,952	409,985	514,698
2012 Notes [Member]
Debt Instrument [Line Items]
Balance at beginning of period	0	133,464
Issuance and exchange	0	0
Payment	0	0
Repurchase	0	(133,464)
Non-cash discount	0
Discount amortization	0	0
Balance at ending of period	0	0
Series 2012 Notes [Member]
Debt Instrument [Line Items]
Balance at beginning of period	0	0
Issuance and exchange	176,679	0
Payment	0	0
Repurchase	0	0
Non-cash discount	(16,833)
Discount amortization	5,682	0	0
Balance at ending of period	165,528	0	0
May 2015 Notes [Member]
Debt Instrument [Line Items]
Balance at beginning of period	138,952	0
Issuance and exchange	0	136,313
Payment	0	0
Repurchase	0	0
Non-cash discount	0
Discount amortization	(4,481)	(2,639)	0
Balance at ending of period	143,433	138,952	0
February 2015 Notes [Member]
Debt Instrument [Line Items]
Balance at beginning of period	177,663	176,964
Issuance and exchange	0	0
Payment	(176,679)	0
Repurchase	0	0
Non-cash discount	0
Discount amortization	7	(699)
Balance at ending of period	991	177,663
Non-recourse Notes [Member]
Debt Instrument [Line Items]
Balance at beginning of period	93,370	204,270
Issuance and exchange	0	0
Payment	(93,370)	(110,900)
Repurchase	0	0
Non-cash discount	0
Discount amortization	0	0
Balance at ending of period	$ 0	$ 93,370