CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - Entity [Domain] - USD ($) $ in Thousands	Total	Common Stock Member	Preferred Stock Member	Additional Paid In Capital Member	Retained Earnings Member	Treasury Stock Member	Accumulated other comprehensive income (loss)
Beginning Balance at Dec. 31, 2013	$ 4,626,150	$ 1,034	$ 50,160	$ 4,170,152	$ 594,430	$ (881)	$ (188,745)
Net Income	(424,905)				(424,905)
Issuance of stock	3,048	1		3,047
Adjustments To Additional Paid In Capital Sharebased Compensation And Exercise Of Stock Options	417			417
Dividends Abstract
Dividends, Preferred Stock, Cash	(1,862)				(1,862)
Stock Issued During Period, Value, Treasury Stock Reissued	11					11
Treasury Stock Value Acquired Cost Method	(872)					(872)
Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent	58,454						58,454
Ending Balance at Jun. 30, 2014	4,260,441	1,035	50,160	4,173,616	167,663	(1,742)	(130,291)
Beginning Balance at Dec. 31, 2014	4,267,382	1,036	50,160	4,196,458	253,717	(4,117)	(229,872)
Net Income	672,278				672,278
Issuance of stock	2,537	1		2,536
Adjustments To Additional Paid In Capital Sharebased Compensation And Exercise Of Stock Options	171			171
Dividends Abstract
Dividends, Preferred Stock, Cash	(1,861)				(1,861)
Stock Issued During Period, Value, Treasury Stock Reissued	46					46
Treasury Stock Value Acquired Cost Method	(1,741)					(1,741)
Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent	10,841						10,841
Ending Balance at Jun. 30, 2015	$ 4,949,653	$ 1,037	$ 50,160	$ 4,199,165	$ 924,134	$ (5,812)	$ (219,031)