Investment Securities AFS Securities Amortized Cost and Fair Value (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Investment securities available for sale:
Investment securities available for sale, amortized cost	$ 5,270,576	$ 4,787,978
Investment securities available for sale, gross unrealized gains	88,043	143,700
Investment securities available for sale, gross unrealized losses	(108,034)	(4,920)
Investment securities available for sale, at fair value	5,250,585	4,926,758
US Treasury Securities [Member]
Investment securities available for sale:
Investment securities available for sale, amortized cost	1,001	1,003
Investment securities available for sale, gross unrealized gains	1	1
Investment securities available for sale, gross unrealized losses	0	0
Investment securities available for sale, at fair value	1,002	1,004
Federal agency securities [Member]
Investment securities available for sale:
Investment securities available for sale, amortized cost		0
Investment securities available for sale, gross unrealized gains		0
Investment securities available for sale, gross unrealized losses		0
Investment securities available for sale, at fair value		0
Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities available for sale:
Investment securities available for sale, amortized cost	653,758	755,644
Investment securities available for sale, gross unrealized gains	23,855	45,599
Investment securities available for sale, gross unrealized losses	(1,533)	(55)
Investment securities available for sale, at fair value	676,080	801,188
Government-Sponsored Enterprise (GSE) Residential Mortgages [Member]
Investment securities available for sale:
Investment securities available for sale, amortized cost	3,855,467	3,708,287
Investment securities available for sale, gross unrealized gains	61,542	93,595
Investment securities available for sale, gross unrealized losses	(78,579)	(3,727)
Investment securities available for sale, at fair value	3,838,430	3,798,155
Private Label Residential Mortgages [Member]
Investment securities available for sale:
Investment securities available for sale, amortized cost	3,035	6,002
Investment securities available for sale, gross unrealized gains	16	147
Investment securities available for sale, gross unrealized losses	(37)	0
Investment securities available for sale, at fair value	3,014	6,149
GSE Commercial Mortgage-Related Securities [Member]
Investment securities available for sale:
Investment securities available for sale, amortized cost	673,555	226,420
Investment securities available for sale, gross unrealized gains	1,764	2,809
Investment securities available for sale, gross unrealized losses	(27,842)	(1,063)
Investment securities available for sale, at fair value	647,477	228,166
Asset-backed Securities [Member]
Investment securities available for sale:
Investment securities available for sale, amortized cost	23,049	0
Investment securities available for sale, gross unrealized gains	10	0
Investment securities available for sale, gross unrealized losses	0	0
Investment securities available for sale, at fair value	23,059	0
Other Debt And Other Equity Securities [Member]
Investment securities available for sale:
Investment securities available for sale, amortized cost	60,711	90,622
Investment securities available for sale, gross unrealized gains	855	1,549
Investment securities available for sale, gross unrealized losses	(43)	(75)
Investment securities available for sale, at fair value	$ 61,523	$ 92,096