Equity - Share Repurchase Program and Share Repurchase Activity (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	May 31, 2015
Stockholders' Equity Note [Abstract]
Stock repurchase program, authorized amount			$ 1,200,000,000
Stock repurchase program, remaining authorized repurchase amount	$ 900,000,000
Number of shares repurchased (in shares)	212,424	239,268
Cash paid for repurchased shares (in thousands)	$ 44,839,000	$ 28,394,000
Treasury stock, average price paid per share (in dollars per share)	$ 140.46	$ 118.73