Consolidated Statements of Shareholder's Equity Statement - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Surplus	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Non-controlling Interests
Balance, beginning of period at Dec. 31, 2012	$ 11,083,573		$ 2,173	$ 15,172,910	$ (4,146,573)	$ 26,058	$ 29,005
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	419,930				417,836		2,094
Other comprehensive income (loss), net of tax	(113,994)					(113,994)
Issuance of common/preferred stock	100,000		34	99,966
Dividends	(2,092)						(2,092)
Vesting of restricted stock	(5,741)			(5,741)
Restricted stock retained to cover taxes	(2,228)			(2,228)
Amortization of stock-based deferred compensation	8,311			8,311
Balance, end of period at Dec. 31, 2013	11,487,759		2,207	15,273,218	(3,728,737)	(87,936)	29,007
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	468,532				466,556		1,976
Other comprehensive income (loss), net of tax	36,579					36,579
Issuance of common/preferred stock	117,000		23	116,977
Dividends	(104,092)			(102,000)			(2,092)
Vesting of restricted stock	(4,702)			(4,702)
Restricted stock retained to cover taxes	(2,507)			(2,507)
Restricted stock tax benefit	490			490
Amortization of stock-based deferred compensation	4,515			4,515
Balance, end of period at Dec. 31, 2014	12,003,574	$ 0	2,230	15,285,991	(3,262,181)	(51,357)	28,891
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	491,795				489,567		2,228
Other comprehensive income (loss), net of tax	(47,950)					(47,950)
Issuance of common/preferred stock	229,475	229,475
Dividends	(97,093)			(95,000)			(2,093)
Vesting of restricted stock	(3,720)			(3,720)
Restricted stock retained to cover taxes	(2,984)			(2,984)
Restricted stock tax benefit	12			12
Amortization of stock-based deferred compensation	4,175			4,175
Balance, end of period at Dec. 31, 2015	$ 12,577,284	$ 229,475	$ 2,230	$ 15,188,474	$ (2,772,614)	$ (99,307)	$ 29,026