Fair Value Disclosures (Details) - Assets And Liabilities Measured At Fair Value On Recurring Basis - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Assets measured at fair value on a recurring basis	$ 93,590	$ 38,264
Level 1
Assets:
Assets measured at fair value on a recurring basis	29,108	10,252
Level 1 | Plan Assets
Assets:
Assets measured at fair value on a recurring basis	29,108	10,252
Level 2
Assets:
Assets measured at fair value on a recurring basis	64,482	28,012
Liabilities:
Liabilities measured at fair value on a recurring basis	929,065	45,909
Level 2 | Foreign Exchange Forward
Assets:
Assets measured at fair value on a recurring basis	2,053	165
Liabilities:
Liabilities measured at fair value on a recurring basis	1,605	485
Level 2 | Interest rate swap
Assets:
Assets measured at fair value on a recurring basis	3,412	0
Liabilities:
Liabilities measured at fair value on a recurring basis	0	2,349
Level 2 | Plan Assets
Assets:
Assets measured at fair value on a recurring basis	59,017	27,847
Level 2 | Plan Liabilities
Liabilities:
Liabilities measured at fair value on a recurring basis	89,900	43,075
Level 2 | Debt | Senior notes
Liabilities:
Liabilities measured at fair value on a recurring basis	$ 837,560	$ 0