Shareholders' Equity - Conversion of Series C Convertible Units into Class A Units (Details) - AH LLC - Series C Convertible Units	Dec. 31, 2016 shares	Feb. 28, 2016 shares	Dec. 31, 2015 shares
Class of Stock [Line Items]
Units owned (in shares)	0		31,085,974
Operating Partnership
Class of Stock [Line Items]
Units owned (in shares)		31,085,974
Business acquisition, equity interest issued or issuable, number of shares, multiplier		1