Investment (Held-to-Maturity) Securities (Details) $ in Thousands		6 Months Ended
		Jun. 30, 2017 USD ($)		Dec. 31, 2016 USD ($)		Jun. 30, 2016 USD ($)
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investments Securities, Amortized Cost		$ 490,426		$ 546,145		$ 560,711
Investment Securities, fair value		515,675		565,493		599,062
Investment Securities, Gross Unrealized Gain		26,092	[1]	21,154	[2]	38,440	[3]
Investment Securities, Gross Unrealized Loss		(843)	[1]	(1,806)	[2]	(89)	[3]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investments Securities, Debt Maturities, Amortized Cost		490,426		546,145		560,711
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair Value		$ 515,675		565,493		599,062
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield		3.73%
Investment Securities, Pledged as Collateral [Abstract]
Investment Securities, Pledged as Collateral, Amortized Cost		$ 251,684		322,208		287,166
Investment Securities, Pledged as Collateral, Fair Value		$ 255,097		$ 323,808		$ 293,625
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		105		193		20
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 123,272		$ 236,070		$ 11,915
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		3,000		5,188		5,236
Investment Securities, Continuous Unrealized Loss Position, Fair Value		126,272		241,258		17,151
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		764		1,709		20
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		79		97		69
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		843		1,806		89
Fixed Maturity Securities [Member]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		104,701
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		168,198
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		141,018
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		58,474
Investment Securities, Debt Maturities, Single Maturity Date, Net Carrying Value		472,391
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		104,918
Investment Securities, Debt Maturities, One to Five Years, Fair Value		171,887
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		159,635
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		60,593
Investment Securities, Debt Maturities, Single Maturity Date, Fair Value		$ 497,033
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		1.95%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		2.89%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.69%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		4.90%
Investment Securities, Debt Maturities, Nominal Yield		3.77%
Investment Securities, Debt Maturities, Weighted Average Maturity	[4]	4.83
Municipal and other tax-exempt securities
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investments Securities, Amortized Cost		$ 267,375		320,364		334,551
Investment Securities, fair value		270,531		321,225		340,700
Investment Securities, Gross Unrealized Gain		3,384	[1]	2,272	[2]	6,234	[3]
Investment Securities, Gross Unrealized Loss		(228)	[1]	(1,411)	[2]	(85)	[3]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		90,415
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		122,560
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		10,739
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		43,661
Investment Securities, Debt Maturities, Single Maturity Date, Net Carrying Value		267,375
Investments Securities, Debt Maturities, Amortized Cost		267,375		320,364		334,551
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		90,436
Investment Securities, Debt Maturities, One to Five Years, Fair Value		122,914
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		11,220
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		45,961
Investment Securities, Debt Maturities, Single Maturity Date, Fair Value		270,531
Investment Securities, Debt Maturities, Fair Value		$ 270,531		$ 321,225		$ 340,700
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield	[5]	1.66%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield	[5]	2.12%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield	[5]	4.88%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield	[5]	5.05%
Investment Securities, Debt Maturities, Nominal Yield	[5]	2.55%
Investment Securities, Debt Maturities, Weighted Average Maturity	[4]	3.48
Investment Securities,Debt Maturities, Effective tax rate for nominal yield calculation		39.00%
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		82		151		19
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 111,078		$ 219,892		$ 11,915
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		3,000		4,333		4,378
Investment Securities, Continuous Unrealized Loss Position, Fair Value		114,078		224,225		16,293
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		149		1,316		20
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		79		95		65
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		228		1,411		85
Other debt securities
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investments Securities, Amortized Cost		205,016		205,004		202,410
Investment Securities, fair value		226,502		222,795		233,129
Investment Securities, Gross Unrealized Gain		22,040	[1]	18,115	[2]	30,723	[3]
Investment Securities, Gross Unrealized Loss		(554)	[1]	(324)	[2]	(4)	[3]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, Less than One Year, Net Carrying Value		14,286
Investment Securities, Debt Maturities, One to Five Years, Net Carrying Value		45,638
Investment Securities, Debt Maturities, Six to Ten Years, Net Carrying Value		130,279
Investment Securities, Debt Maturities, Over Ten Years, Net Carrying Value		14,813
Investment Securities, Debt Maturities, Single Maturity Date, Net Carrying Value		205,016
Investments Securities, Debt Maturities, Amortized Cost		205,016		205,004		202,410
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Fair Value		14,482
Investment Securities, Debt Maturities, One to Five Years, Fair Value		48,973
Investment Securities, Debt Maturities, Six to Ten Years, Fair Value		148,415
Investment Securities, Debt Maturities, Over Ten Years, Fair Value		14,632
Investment Securities, Debt Maturities, Single Maturity Date, Fair Value		226,502
Investment Securities, Debt Maturities, Fair Value		$ 226,502		$ 222,795		$ 233,129
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Less Than One Year, Nominal Yield		3.84%
Investment Securities, Debt Maturities, One to Five Years, Nominal Yield		4.95%
Investment Securities, Debt Maturities, Six to Ten Years, Nominal Yield		5.75%
Investment Securities, Debt Maturities, Over Ten Years, Nominal Yield		4.46%
Investment Securities, Debt Maturities, Nominal Yield		5.35%
Investment Securities, Debt Maturities, Weighted Average Maturity	[4]	6.59
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		22		41		1
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 8,384		$ 11,820		$ 0
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0		855		858
Investment Securities, Continuous Unrealized Loss Position, Fair Value		8,384		12,675		858
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		554		322		0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0		2		4
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		554		324		4
U.S. government agency residential mortgage-backed securities
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investment Securities, Debt Maturities, without Single Maturity Date, Net Carrying Value		18,035
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, without Single Maturity Date, Fair Value		$ 18,642
Investment Securities, Debt Maturities, Nominal Yield [Abstract]
Investment Securities, Debt Maturities, Nominal Yield	[6]	2.76%
Investment Securities, Debt Maturities, Average Expected Life of Mortgage-backed Securities		4 years 255 days
U.S. government agency residential mortgage-backed securities | Other
Schedule of Investment (Held-to-Maturity) Securities [Line Items]
Investments Securities, Amortized Cost		$ 18,035		20,777		23,750
Investment Securities, fair value		18,642		21,473		25,233
Investment Securities, Gross Unrealized Gain		668	[1]	767	[2]	1,483	[3]
Investment Securities, Gross Unrealized Loss		(61)	[1]	(71)	[2]	0	[3]
Investment Securities, Debt Maturities, Net Carrying Value [Abstract]
Investments Securities, Debt Maturities, Amortized Cost		18,035		20,777		23,750
Investment Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Investment Securities, Debt Maturities, Fair Value		$ 18,642		$ 21,473		$ 25,233
Investment Securities, Continuous Unrealized Loss Position, Qualitative Disclosure [Abstract]
Investment Securities, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions		1		1		0
Investment Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		$ 3,810		$ 4,358		$ 0
Investment Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		0		0		0
Investment Securities, Continuous Unrealized Loss Position, Fair Value		3,810		4,358		0
Investment Securities, Continuous Unrealized Loss Position, Aggregate Losses [Abstract]
Investment Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		61		71		0
Investment Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		0		0		0
Investment Securities, Continuous Unrealized Loss Position, Accumulated Loss		$ 61		$ 71		$ 0

[1] Gross unrealized gains and losses are not recognized in Accumulated Other Comprehensive Income "AOCI" in the Consolidated Balance Sheets.

[2] Gross unrealized gains and losses are not recognized in AOCI in the Consolidated Balance Sheets.

[3] Gross unrealized gains and losses are not recognized in AOCI in the Consolidated Balance Sheets.

[4] Expected maturities may differ from contractual maturities, because borrowers may have the right to call or prepay obligations with or without penalty.

[5] Calculated on a taxable equivalent basis using a 39 percent effective tax rate.

[6] The nominal yield on residential mortgage-backed securities is based upon prepayment assumptions at the purchase date. Actual yields earned may differ significantly based upon actual prepayments. See Quarterly Financial Summary - Unaudited for current yields on the investment securities portfolio.