Fair Value Measurement Fair Value Measurement (Reconciliation of Level 3 Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Balance, end of period	$ 335,979	$ 546,858	$ 335,979	$ 546,858
Level 3
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances	17,499	537,930	34,999	537,930
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Balance, beginning of period	286,874	0	263,317	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ 31,606	$ 8,928	$ 37,663	$ 8,928