Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Other Comprehensive Income [Abstract]
Net income	$ 385,721	$ 39,133	$ (224,282)
Other comprehensive income (loss):
Change in unrealized gains on investments and MBS available-for-sale	16,119	86,140	(6,541)
Realized net gains reclassified from other comprehensive income	(17,016)	(18,462)	(25,745)
Less deferred income tax provision	494	(2,384)	11,823
Net other comprehensive income (loss)	(403)	65,294	(20,463)
Comprehensive income	$ 385,318	$ 104,427	$ (244,745)