Subsequent Events Subsequent Event (Details) - Interest Rate Swaps 2020-2033 [Member] - Subsequent Event [Member] $ in Millions	Feb. 15, 2018 USD ($)
Subsequent Event [Line Items]
Average fixed interest rate on interest rate swap	5.19%
Minimum [Member]
Subsequent Event [Line Items]
Derivative, notional amount	$ 80
Maximum [Member]
Subsequent Event [Line Items]
Derivative, notional amount	$ 425

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

No definition available.

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration