Stockholders' Equity and EPS - Reclassifications out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification adjustment for gains included in net income	$ 23,270	$ 24,975	$ 18,586	$ 58,238
Related tax expense	(65,047)	(54,974)	(118,631)	(118,040)
Net income available to common stockholders	92,964	86,143	172,138	174,659
Reclassification out of Accumulated Other Comprehensive Income | Gains on investment securities, net
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification adjustment for gains included in net income	(12,328)	(141)	(11,582)	(2,737)
Related tax expense	5,017	57	4,713	1,105
Net income available to common stockholders	$ (7,311)	$ (84)	$ (6,869)	$ (1,632)