Shareholders' Equity (Details) (USD $)	1 Months Ended	2 Months Ended	3 Months Ended												12 Months Ended					1 Months Ended
	Jun. 30, 2013	Feb. 26, 2015	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Jul. 31, 2013	Nov. 06, 2014	Jul. 02, 2013
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount																					$ 500,000,000
Stock Repurchased During Period, Shares		0
Other IPO Related Expenses																	2,400,000	[1]
Employee Stock Purchase Plan, discount to market price, percent															5.00%
Equity-based compensation expense															16,400,000		46,600,000		22,100,000
Proceeds from shares sold by certain selling stockholders															0
Preferred Stock, Shares Issued			0								0				0		0
Secondary-offering related expenses			200,000		300,000		500,000		400,000						1,400,000	[1]	600,000
Proceeds from Issuance Initial Public Offering																	424,700,000
Stockholders' Equity Note, Stock Split, Conversion Ratio	143.0299613
Common Stock, Par Value			$ 0.01								$ 0.01				$ 0.01		$ 0.01
Preferred Stock, Shares Authorized			100,000,000								100,000,000				100,000,000		100,000,000
Preferred Stock, Par or Stated Value Per Share			$ 0.01								$ 0.01				$ 0.01		$ 0.01
Preferred Stock, Shares Outstanding			0								0				0		0
Common Stock, Shares Authorized			1,000,000,000								1,000,000,000				1,000,000,000		1,000,000,000
Common Stock, Dividends, Per Share, Cash Paid			$ 0.0675		$ 0.0425		$ 0.0425		$ 0.0425		$ 0.0425	$ 0.0000	$ 0.0000	$ 0.0000
Dividends, Common Stock, Cash			11,700,000		7,300,000		7,300,000		7,300,000		7,300,000	0	0	0
Coworker Stock Purchase Plan [Member]
Class of Stock [Line Items]
Equity-based compensation expense															$ 0.0
IPO [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues																				23,250,000
Share Price																						$ 17.00
IPO Over-allotment [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues																	3,487,500
Secondary Offering [Member]
Class of Stock [Line Items]
Shares sold by certain selling stockholders			15,000,000		15,000,000		15,000,000		10,000,000								15,000,000
Secondary offering over-allotment [Member]
Class of Stock [Line Items]
Shares sold by certain selling stockholders			2,250,000	[2]	0	[2],[3]	2,250,000	[2]	1,500,000	[2]							2,250,000	[2]

[1] Other expenses include secondary-offering expenses of $1.4 million and $0.6 million for the years ended December 31, 2014 and 2013, respectively.

[2] Under each underwriting agreement, the selling stockholders granted the underwriters an option, exercisable for thirty days, to purchase up to the additional amount of shares noted.

[3] The option to purchase additional shares was not exercised in connection with the September 2014 secondary offering