Fair Value Measurements, Call Option FV Assumption Table (Details) (USD $)	3 Months Ended		12 Months Ended
	Dec. 31, 2012 basispoints		Dec. 31, 2012 basispoints		Dec. 31, 2011	Dec. 31, 2010
Fair Value Disclosures [Abstract]
Stock price at December 31, 2012	$ 61.69		$ 61.69
Quarterly dividend yield (per share)			$ 0.24	[1]
Risk-free interest rate			0.28%	[2]
Credit spread (basis points)	246	[3]	246	[3]
Expected volatility rate			20.40%	[4]
Quarterly cash dividends	$ 0.25		$ 1.00		$ 0.96	$ 0.96
Two-year Constant Maturity Treasury rate	2 years		2 years
Three-year Constant Maturity Treasury rate	3 years		3 years

[1] Quarterly dividends during 2012 were $0.25 per share, but the model assumes a discrete $0.24 per share quarterly dividend as was paid at the inception of the Call Options. Quarterly dividends in excess of $0.24 per share do not affect the Call Options' value due to anti-dilution adjustments.

[2] The risk-free rate was based on the two-year Constant Maturity Treasury rate and three-year Constant MaturityTreasury rate on December 31, 2012, compounded semi-annually.

[3] The credit spread is based on the Company's long-term credit rating of BB- issued by Standard & Poor’s and a seniorunsecured credit rating of Ba3 issued by Moody’s.

[4] The volatility rate was based on both observed volatility, which is based on the Company’s historical stock price, andimplied volatility from the Company’s traded options. Such volatility was further adjusted to take into considerationmarket participant risk tolerance.