Parent Company Only Financials Statement of Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
INCOME
Interest income on notes receivable	$ 598,582	$ 587,526	$ 595,965
Total revenue	971,286	958,642	939,282
EXPENSE
Personnel expense	390,399	397,015	381,404
Income (loss) before income tax benefit and equity in undistributed net income (loss) of subsidiaries	276,045	267,893	254,459
Income tax expense	85,536	79,201	75,486
Net income	190,509	188,692	178,973
Preferred stock dividends and discount accretion	(5,002)	(5,158)	(5,200)
Net income (loss) available to common equity	185,507	183,534	173,773
Parent Company [Member]
INCOME
Dividends from subsidiaries	223,000	262,000	169,500
Interest income on notes receivable	1,264	1,988	1,807
Other Income	9,682	7,742	5,762
Total revenue	233,946	271,730	177,069
EXPENSE
Interest expense on short and long-term funding	24,847	27,167	35,920
Other expense	745	8,029	14,055
Total expense	(25,592)	(35,196)	(49,975)
Income (loss) before income tax benefit and equity in undistributed net income (loss) of subsidiaries	208,354	236,534	127,094
Income tax expense	(5,801)	(7,086)	(17,948)
Income (loss) before equity in undistributed net income (loss) of subsidiaries	214,155	243,620	145,042
Equity in undistributed net income (loss) of subsidiaries	(23,646)	(54,928)	33,931
Net income	190,509	188,692	178,973
Preferred stock dividends and discount accretion	(5,002)	(5,158)	(5,200)
Net income (loss) available to common equity	$ 185,507	$ 183,534	$ 173,773