Employee Benefit Plans (Details 13) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Assets Category:
Fair value	$ 276.8
NAV [Member]
Assets Category:
Fair value	272.3		242.4
Commingled Pools / Collective Trusts [Member] | U S equity [Member]
Assets Category:
Fair value	36.7		33.4	[1]
Commingled Pools / Collective Trusts [Member] | International equity [Member]
Assets Category:
Fair value	60.3	[2]	48.3	[2]
Redemption Frequency (if currently eligible)	Monthly	[2]	Monthly	[2]
Redemption Notice Period	10 - 15 days	[2]	10 - 15 days	[2]
Commingled Pools / Collective Trusts [Member] | Fixed income [Member]
Assets Category:
Fair value	85.3	[3]	81.9	[3]
Redemption Frequency (if currently eligible)	Quarterly	[3]	Quarterly	[3]
Redemption Notice Period	15 days	[3]	15 days	[3]
Mutual Funds [Member] | U S equity [Member]
Assets Category:
Fair value	47.3	[4]	38.8	[4]
Mutual Funds [Member] | International equity [Member]
Assets Category:
Fair value	3.9	[4]	4.4	[4]
Mutual Funds [Member] | Fixed income [Member]
Assets Category:
Fair value	7.8	[5]	8.4	[5]
Balanced pension trusts [Member] | U S equity [Member]
Assets Category:
Fair value	2.4	[6]	2.1	[6]
Redemption Frequency (if currently eligible)	Daily	[6]	Daily	[6]
Redemption Notice Period	5 days	[6]	5 days	[6]
Balanced pension trusts [Member] | International equity [Member]
Assets Category:
Fair value	7.9	[6]	6.5	[6]
Redemption Frequency (if currently eligible)	Daily	[6]	Daily	[6]
Redemption Notice Period	5 days	[6]	5 days	[6]
Balanced pension trusts [Member] | Fixed income [Member]
Assets Category:
Fair value	6.6	[6]	6.5	[6]
Redemption Frequency (if currently eligible)	Daily	[6]	Daily	[6]
Redemption Notice Period	5 days	[6]	5 days	[6]
Pension fund [Member]
Assets Category:
Fair value			242.6
Pension fund [Member] | U S equity [Member]
Assets Category:
Fair value	1.3	[7]	1.1	[7]
Redemption Frequency (if currently eligible)	Daily	[7]	Daily	[7]
Redemption Notice Period	7 days	[7]	7 days	[7]
Pension fund [Member] | International equity [Member]
Assets Category:
Fair value	6.7	[7]	5.5	[7]
Redemption Frequency (if currently eligible)	Daily	[7]	Daily	[7]
Redemption Notice Period	7 days	[7]	7 days	[7]
Pension fund [Member] | Fixed income [Member]
Assets Category:
Fair value	6.1	[8]	4.8	[8]
Redemption Frequency (if currently eligible)	Daily	[8]	Daily	[8]
Redemption Notice Period	7 days	[8]	7 days	[8]
Pension fund [Member] | Money Market Funds [Member]
Assets Category:
Fair value			$ 0.7	[9]
Redemption Frequency (if currently eligible)			Daily	[9]
Redemption Notice Period			7 days	[9]

[1] This category includes investments primarily in U.S. equity securities that include large, mid and small capitalization companies.

[2] This category includes investments primarily in non-U.S. equity securities that include large, mid and small capitalization companies in large developed markets as well as emerging markets equities.

[3] This category includes investments in U.S. investment grade and high yield fixed income securities, non-U.S. fixed income securities and emerging markets fixed income securities.

[4] These funds seek capital appreciation and generally invest in common stocks of U.S. and non-U.S. issuers. They may invest in growth stocks or value stocks.

[5] This fund seeks to provide inflation protection. It currently invests at least 80% of its assets in inflation-indexed bonds issued by the U.S. government. It may invest in bonds of any maturity, though the fund typically maintains a dollar-weighted average maturity of 7 to 20 years.

[6] The investment objectives of the fund are to provide long-term capital growth and income by investing primarily in a well-diversified, balanced portfolio of Canadian common stocks, bonds and money market securities. The fund also holds a portion of its assets in U.S. and non-U.S. equities.

[7] This category includes investments in U.S. and non-U.S. equity securities and aims to provide returns consistent with the markets in which it invests and provide broad exposure to countries around the world.

[8] This category includes investments in U.K. government index-linked securities (index-linked gilts) that have maturity periods of 5 years or longer and investment grade corporate bonds denominated in sterling.

[9] This fund invests in U.K. money market instruments and includes cash, bank deposits and short-term fixed interest investments.