Stockholder's Equity - Shares of Common Stock Issued Under Employee Stock Purchase Plan (Details) - $ / shares	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Number of shares available, beginning balance (in shares)			152,344
Shares issued during period (in shares)	5,360	4,301	5,357
Number of shares available, ending balance (in shares)	137,326
Per share price of shares issued during period (in dollars per share)	$ 113.60	$ 105.36	$ 89.19