Short-Term Borrowings and Long-Term Debt Repurchase Agreements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Short-term Debt [Line Items]
Short-term Debt	$ 1,258,629	$ 868,399	$ 597,033
Repurchase Agreements [Member]
Short-term Debt [Line Items]
Short-term Debt	175,621	156,238	186,735
Short-term Debt, Weighted Average Interest Rate	0.12%	0.16%	0.12%
Short-term Debt, Average Outstanding Amount	$ 186,851	$ 206,842	$ 208,144
Debt Instrument, Interest Rate During Period	0.11%	0.12%	0.13%