Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 57,607	$ 58,883	$ 159,520	$ 95,076
Available for sale securities:
Unrealized gains (losses) arising during the period	15,258	(8,862)	3,695	21,052
Reclassification adjustment for net gains realized in earnings (net of tax expense of $88 and $361 for the three months ended September 30, 2015 and 2014, respectively, and net of tax expense of $142 and $751 for the nine months ended September 30, 2015 and 2014, respectively)	(132)	(542)	(213)	(1,127)
Income tax (expense) benefit related to unrealized gains	(6,103)	3,545	(1,478)	(8,421)
Net change in unrealized gains (losses)	9,023	(5,859)	2,004	11,504
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 $37 for the nine months ended September 30, 2014)	0	0	0	57
Net change in unrealized losses related to factors other than credit	0	0	0	57
Other comprehensive income (loss), net of tax	9,023	(5,859)	2,004	11,561
Comprehensive income	$ 66,630	$ 53,024	$ 161,524	$ 106,637