Benefit Plans and Other Postretirement Benefits - Defined Contribution (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Benefit Plans and Other Postretirement Benefits
Contributions to U.S. defined contribution plans by the Company, maximum percentage of eligible compensation	5.00%
Matching contributions to U.S. defined contribution plans by the Company	$ 5.0	$ 4.2	$ 3.8

The amount of the cost recognized during the period for defined contribution plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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