Investment Securities - Debt Maturities (Details) (Investment Securities [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Investment Securities [Member]
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
Available-for-sale Securities, Due within one year, Amortized Cost	$ 1,014,587
Available-for-sale Securities, Due after one year through five years, Amortized Cost	156,022
Available-for-sale Securities, Due after five years through ten years, Amortized Cost	261,556
Available-for-sale Securities, Due after ten years, Amortized Cost	507,542
Available-for-sale Securities, Debt Maturities, Single Maturity Date [Abstract]
Available-for-sale Securities, Due within one year, Fair Value	1,014,679
Available-for-sale Securities, Due after one year through five years, Fair Value	156,719
Available-for-sale Securities, Due after five years through ten years, Fair Value	262,917
Available-for-sale Securities, Due after ten years, Fair Value	504,184
Available-for-sale securities	$ 1,938,499	$ 2,483,147
Available-for-sale Securities, Debt Maturities, Weighted Average Yield, Single Maturity Date [Abstract]
Available-for-sale Securities, Due within one year, Weighted-Average Yield	0.30%
Available-for-sale Securities, Due after one year through five years, Weighted-Average Yield	0.87%
Available-for-sale Securities, Due after five years through ten years, Weighted-Average Yield	0.85%
Available-for-sale Securities, Due after ten years, Weighted-Average Yield	1.00%
Available-for-sale Securities, Total Weighted-Average Yield	0.60%

Available-for-sale Securities, Debt Maturities, after Ten Years, Weighted-Average Yield

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- Definition

Available-for-sale Securities, Debt Maturities, Next Twelve Months, Weighted-Average Yield

+ References

No definition available.

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- Definition

Available-for-sale Securities, Debt Maturities, Weighted-Average Yield

+ References

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- Definition

Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Weighted-Average Yield

+ References

No definition available.

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- Definition

Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted-Average Yield

+ References

No definition available.

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

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Amount after adjustments of available-for-sale debt securities at cost, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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Fair value of available-for-sale debt securities maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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- Definition

Amount after adjustments of available-for-sale debt securities at cost, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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-Name Accounting Standards Codification

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Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Amount after adjustments of available-for-sale debt securities at cost, maturing after the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Fair value of available-for-sale debt securities maturing after the tenth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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- Definition

Amount after adjustments of available-for-sale debt securities at cost, maturing in the next fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings less cumulative-effect adjustments, and fair value hedge accounting adjustments. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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-Name Accounting Standards Codification

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- Definition

Fair value of available-for-sale debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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