Fair Value Measurements (Narrative) (Details) (USD $)	9 Months Ended	0 Months Ended			9 Months Ended	1 Months Ended	9 Months Ended
	Sep. 30, 2014	Apr. 30, 2014 ARS [Member]	Mar. 31, 2014 ARS [Member]	Dec. 31, 2013 ARS [Member]	Sep. 30, 2014 Term Loan [Member]	Jan. 31, 2012 Term Loan [Member] Swap [Member]	Sep. 30, 2014 Term Loan [Member] Swap [Member]	Sep. 30, 2014 Fair value [Member] Senior unsecured notes [Member]	Dec. 31, 2013 Fair value [Member] Senior unsecured notes [Member]	Sep. 30, 2014 Carrying value [Member] Senior unsecured notes [Member]	Dec. 31, 2013 Carrying value [Member] Senior unsecured notes [Member]	Sep. 30, 2014 Carrying value [Member] Other long-term debt [Member]	Dec. 31, 2013 Carrying value [Member] Other long-term debt [Member]
Long-term Debt
Debt								$ 312,200,000	$ 321,000,000	$ 298,700,000	$ 298,500,000	$ 646,800,000	$ 435,400,000
Face amount					250,000,000	200,000,000
Term of debt						5 years
Maturity date					Jun. 05, 2019
Debt Instrument, Issuance Date					Jun. 05, 2014		Jun. 05, 2014
Investments
Investment in auction rate securities			46,300,000	46,300,000
Proceeds from Sale of Available-for-sale Securities, Debt	44,497,000	44,500,000
Loss on sale of investments	$ 1,786,000