Components of Company's Interest Income and Interest Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Interest income:
Investment Securities	$ 614,419		$ 723,750
Commercial investment portfolio	39,486	[1]	1,070	[1]
U.S. Treasury securities	1,329		5,996
Securities loaned	114		2,612
Reverse repurchase agreements	500		3,636
Other	53		153
Total interest income	655,901		737,217
Interest expense:
Repurchase agreements	103,131		157,064
Convertible Senior Notes	18,897		15,813
U.S. Treasury securities sold, not yet purchased	1,076		2,788
Securities borrowed	95		1,925
Securitized debt of consolidated VIE	1,611
Participation sold	161
Total interest expense	124,971		177,590
Net interest income	$ 530,930		$ 559,627

[1] Includes commercial real estate debt and preferred equity and corporate debt.