Commitments and Contingencies, purchase commitments (Details) (BOSS Installation, USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2012
BOSS Installation
Long-term Purchase Commitment [Line Items]
Purchase commitment required payments	$ 148.5
Purchase commitment required payments made	$ 67.4

The minimum amount the entity agreed to spend under the long-term purchase commitment.

No definition available.

Name:	us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration