Consolidating Financial Statements - Narrative (Details) (USD $)	1 Months Ended
	Aug. 31, 2009	Mar. 31, 2012	Dec. 31, 2014		Dec. 31, 2013
Senior Exchangeable Notes due 2015 at a fixed interest rate of 4.50% [Member]
Debt Instrument [Line Items]
Issuance date of debt instrument	August 2009
Face amount	$ 172,500,000.0		$ 130,973,000		$ 130,973,000
Fixed interest rate	4.50%		4.50%	[1]
Maturity date description	August 2015
Senior Notes due 2022 at a fixed interest rate of 3.75% [Member]
Debt Instrument [Line Items]
Issuance date of debt instrument		March 2012
Face amount		$ 325,000,000
Fixed interest rate		3.75%	3.75%
Maturity date description		2022

[1] Our Senior Exchangeable Notes maturing in 2015 were discounted by $1.3 million and $3.2 million as of December 31, 2014 and 2013, respectively. Upon maturity the liability will be $131 million.