Summary of Significant Accounting Policies - Goodwill and Other Intangibles (Details)	12 Months Ended
	Dec. 31, 2016
Software development cost
Finite-Lived Intangible Assets [Line Items]
Useful life	5 years
Software acquired | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	3 years
Software acquired | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	10 years
Other intangible assets excluding trade name | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful life	3 years
Other intangible assets excluding trade name | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful life	25 years