Statement of Comprehensive Income Statement of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 90,974	$ 57,452	$ 253,761	$ 181,373
Income Tax Expense (Benefit)	27,076	16,737	76,889	54,863
Net income	63,898	40,715	176,872	126,510
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax	(16,207)	(17,491)	24,293	(104,853)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	(5,672)	(6,123)	8,503	(36,699)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	(10,535)	(11,368)	15,790	(68,154)
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, before Tax	(563)	(534)	(1,551)	(1,654)
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Tax	(197)	(187)	(543)	(579)
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	(366)	(347)	(1,008)	(1,075)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	14	(1)	150	2,802
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	5	0	53	981
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	(9)	1	(97)	(1,821)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax	(16,784)	(18,026)	22,592	(103,705)
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax	(5,874)	(6,310)	7,907	(36,297)
Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax	(10,910)	(11,716)	14,685	(67,408)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, before Tax	0	0	0	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	0	0	0	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Net of Tax	0	0	0	0
Other Comprehensive Income Defined benefit plan, amortization of gains, before tax	768	0	2,398	0
Other comprehensive Income, Defined Benefit Plan, Amortization of Gains, tax	269	0	839	0
Other Comprehensive Income, Defined benefit plan, amortization of gains, after tax	499	0	1,559	0
Other Comprehensive (Income) Loss, Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service Cost (Credit), before Tax	516	0	1,614	0
Other Comprehensive Income (Loss), Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service (Cost) Credit, Tax	181	0	565	0
Other Comprehensive Income (Loss), Amortization Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Prior Service (Cost) Credit, Net of Tax	335	0	1,049	0
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, before Tax	1,284	0	4,012	0
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Tax	450	0	1,404	0	20,233
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	834	0	2,608	0
Other Comprehensive Income (Loss), before Tax	(15,500)	(18,026)	26,604	(103,705)
Other Comprehensive Income (Loss), Tax	(5,424)	(6,310)	9,311	(36,297)
Other Comprehensive Income (Loss), Net of Tax	(10,076)	(11,716)	17,293	(67,408)
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent	75,474	39,426	280,365	77,668
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	21,652	10,427	86,200	18,566
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 53,822	$ 28,999	$ 194,165	$ 59,102