Debt - Line of Credit (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Oct. 27, 2014
Line of Credit Facility [Line Items]
Line of Credit Facility, Available Additional Borrowing Capacity	$ 300
Payments of Financing Costs	1.6
Line of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		500
Credit Agreement [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 300
Credit Agreement [Member] | Adjusted Base Rate Advances [Member] | Adjusted Base Rate [Member] | Federal Funds Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate		0.50%
Credit Agreement [Member] | Adjusted Base Rate Advances [Member] | Adjusted Base Rate [Member] | Eurodollar Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate		1.00%
Credit Agreement [Member] | Adjusted Base Rate Advances [Member] | Applicable Margin [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate		0.125%
oii term loan facility spread on variable rate		0.00%
Credit Agreement [Member] | Adjusted Base Rate Advances [Member] | Applicable Margin [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate		0.75%
oii term loan facility spread on variable rate		0.50%
Credit Agreement [Member] | Eurodollar Advances [Member] | Applicable Margin [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate		1.125%
oii term loan facility spread on variable rate		1.00%
Credit Agreement [Member] | Eurodollar Advances [Member] | Applicable Margin [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Basis Spread on Variable Rate		1.75%
oii term loan facility spread on variable rate		1.50%