Summary of Unaudited Pro Forma Financial Information (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Business Combinations [Abstract]
Adjustment of redeemable noncontrolling interest to estimated redemption value	$ 20.2	$ 0.0

Amount of decrease to net income for accretion of temporary equity to its redemption value to derive net income apportioned to common stockholders.

No definition available.

Name:	us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration