Fair Value Measurements Fair Value Measurements (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans Receivable, Fair Value Disclosure	$ 12,280,982	$ 11,757,951
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Net Gain (Loss) from Nonrecurring Assets	(9,316)
Non Purchased Credit Impaired Loans and Leases [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Net Gain (Loss) from Nonrecurring Assets	(9,192)
Other real estate and foreclosed assets [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total Net Gain (Loss) from Nonrecurring Assets	$ (124)