Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 17,221	$ 26,253	$ 35,985	$ 49,614
Available for sale securities:
Unrealized gains (losses) arising during the period	21,936	(36,793)	29,914	(41,220)
Reclassification adjustment for net gains realized in earnings (net of tax expense of $375 and $3 for the three months ended June 30, 2014 and 2013, respectively, and net of tax expense of $375 thousand and $6 for the six months ended June 30, 2014 and 2013, respectively)	(585)	(5)	(585)	(9)
Income tax (expense) benefit related to unrealized gains (losses)	(8,775)	14,717	(11,966)	16,488
Net change in unrealized gains	12,576	(22,081)	17,363	(24,741)
Held to maturity securities:
Accretion of unrealized losses related to factors other than credit to investment securities held to maturity (net of tax benefit of $31 and $10 for the three months ended June 30, 2014 and 2013, respectively, and net of tax benefit of $37 and $21 for the six months ended June 30, 2014 and 2013, respectively)	47	14	57	32
Net change in unrealized losses related to factors other than credit	47	14	57	32
Other comprehensive income (loss), net of tax	12,623	(22,067)	17,420	(24,709)
Comprehensive income	$ 29,844	$ 4,186	$ 53,405	$ 24,905