Shareholders' Equity - Conversion of Series C Convertible Units into Class A Units (Details) - AH LLC - Series C Convertible Units	Sep. 30, 2016 shares	Feb. 28, 2016 shares	Dec. 31, 2015 shares
Class of Stock [Line Items]
Ownership units owned (in shares)	0		31,085,974
Operating Partnership
Class of Stock [Line Items]
Ownership units owned (in shares)	0	31,085,974	31,085,974
Ownership units exchange ratio		1