Fair Value of Financial Instruments - Quantitative information about unobservable inputs for material assets and liabilities measured using fair value (Details) - USD ($)		3 Months Ended
		Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Investment securities held to maturity, estimated fair value		$ 1,201,832,000	$ 1,244,121,000
OREO, fair value		17,877,000		$ 17,764,000
Fair Value, measurements, recurring | Other Trading Assets
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Other trading asset, fair value		1,071,000
Fair Value, measurements, recurring | Interest rate contracts
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Interest rate contracts, fair value		3,696,000
Fair Value, measurements, recurring | Other Assets
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Other assets -MSRs, fair value		40,717,000
Fair Value, measurements, nonrecurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Investment securities held to maturity, estimated fair value				3,205,000
Impaired loans, fair value	[1]	69,032,000		132,336,000
Fair Value, Inputs, Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Investment securities held to maturity, estimated fair value		$ 1,201,832,000	$ 1,244,121,000
Fair Value, Inputs, Level 3 | Fair Value, measurements, recurring | Minimum | Other Trading Assets | Discounted cash flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Prepayment rate		5.70%
Fair Value, Inputs, Level 3 | Fair Value, measurements, recurring | Minimum | Interest rate contracts | Discounted cash flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Closing rate		3.70%
Cap grid rate		0.30%
Fair Value, Inputs, Level 3 | Fair Value, measurements, recurring | Minimum | Other Assets | Discounted cash flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Prepayment rate		1.80%
Cost to service		$ 65
Discount rate		6.10%
Fair Value, Inputs, Level 3 | Fair Value, measurements, recurring | Maximum | Other Trading Assets | Discounted cash flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Prepayment rate		9.80%
Fair Value, Inputs, Level 3 | Fair Value, measurements, recurring | Maximum | Interest rate contracts | Discounted cash flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Closing rate		99.40%
Cap grid rate		2.30%
Fair Value, Inputs, Level 3 | Fair Value, measurements, recurring | Maximum | Other Assets | Discounted cash flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Prepayment rate		56.80%
Cost to service		$ 4,000
Discount rate		18.60%
Fair Value, Inputs, Level 3 | Fair Value, measurements, recurring | Average | Other Trading Assets | Discounted cash flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Default rate		10.50%
Prepayment rate		7.50%
Fair Value, Inputs, Level 3 | Fair Value, measurements, recurring | Average | Interest rate contracts | Discounted cash flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Closing rate		62.10%
Cap grid rate		1.10%
Fair Value, Inputs, Level 3 | Fair Value, measurements, recurring | Average | Other Assets | Discounted cash flow
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Prepayment rate		10.80%
Cost to service		$ 88
Discount rate		8.10%
Fair Value, Inputs, Level 3 | Fair Value, measurements, nonrecurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Investment securities held to maturity, estimated fair value				3,205,000
Impaired loans, fair value	[1]	$ 69,032,000		132,336,000
OREO, fair value		$ 17,877,000		$ 17,764,000
Fair Value, Inputs, Level 3 | Fair Value, measurements, nonrecurring | Minimum | Impaired loans | Appraised value
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Appraised value rate		0.00%
Fair Value, Inputs, Level 3 | Fair Value, measurements, nonrecurring | Maximum | Impaired loans | Appraised value
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Appraised value rate		100.00%
Fair Value, Inputs, Level 3 | Fair Value, measurements, nonrecurring | Average | Impaired loans | Appraised value
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Appraised value rate		33.00%
Fair Value, Inputs, Level 3 | Fair Value, measurements, nonrecurring | Average | OREO | Appraised value
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Appraised value rate	[2]	8.00%

[1] Total gains (losses) represent charge-offs on impaired loans for which adjustments are based on the appraised value of the collateral.

[2] Represents discount to appraised value for estimated costs to sell.